// -*- C++ -*-
//===------------------------ type_traits ---------------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

// STL common functionality
//
// Some aspects of STL are core language concepts that should be used from all C++ code, regardless
// of whether exceptions are enabled in the component.  Common library code that expects to be used
// from exception-free components want these concepts, but including <type_traits> directly introduces
// friction as it requires components not using STL to declare their STL version.  Doing so creates
// ambiguity around whether STL use is safe in a particular component and implicitly brings in
// a long list of headers (including <new>) which can create further ambiguity around throwing new
// support (some routines pulled in may expect it).  Secondarily, pulling in these headers also has
// the potential to create naming conflicts or other implied dependencies.
//
// To promote the use of these core language concepts outside of STL-based binaries, this file is
// selectively pulling those concepts *directly* from corresponding STL headers.  The corresponding
// "std::" namespace STL functions and types should be preferred over these in code that is bound to
// STL.  The implementation and naming of all functions are taken directly from STL, instead using
// "wistd" (Windows Implementation std) as the namespace.
//
// Routines in this namespace should always be considered a reflection of the *current* STL implementation
// of those routines.  Updates from STL should be taken, but no "bugs" should be fixed here.
//
// New, exception-based code should not use this namespace, but instead should prefer the std:: implementation.
// Only code that is not exception-based and libraries that expect to be utilized across both exception
// and non-exception based code should utilize this functionality.

#ifndef _WISTD_TYPE_TRAITS_H_
#define _WISTD_TYPE_TRAITS_H_

// DO NOT add *any* additional includes to this file -- there should be no dependencies from its usage
#include "wistd_config.h"

#if !defined(__WI_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#pragma GCC system_header
#endif

/// @cond
namespace wistd     // ("Windows Implementation" std)
{
    template <class _T1, class _T2> struct __WI_LIBCPP_TEMPLATE_VIS pair;
    template <class _Tp> class __WI_LIBCPP_TEMPLATE_VIS reference_wrapper;
    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS hash;

    template <class>
    struct __void_t { typedef void type; };

    template <class _Tp>
    struct __identity { typedef _Tp type; };

    template <class _Tp, bool>
    struct __WI_LIBCPP_TEMPLATE_VIS __dependent_type : public _Tp {};

    template <bool _Bp, class _If, class _Then>
        struct __WI_LIBCPP_TEMPLATE_VIS conditional {typedef _If type;};
    template <class _If, class _Then>
        struct __WI_LIBCPP_TEMPLATE_VIS conditional<false, _If, _Then> {typedef _Then type;};

#if __WI_LIBCPP_STD_VER > 11
    template <bool _Bp, class _If, class _Then> using conditional_t = typename conditional<_Bp, _If, _Then>::type;
#endif

    template <bool, class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS __lazy_enable_if {};
    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS __lazy_enable_if<true, _Tp> {typedef typename _Tp::type type;};

    template <bool, class _Tp = void> struct __WI_LIBCPP_TEMPLATE_VIS enable_if {};
    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS enable_if<true, _Tp> {typedef _Tp type;};

#if __WI_LIBCPP_STD_VER > 11
    template <bool _Bp, class _Tp = void> using enable_if_t = typename enable_if<_Bp, _Tp>::type;
#endif

    // addressof
#ifndef __WI_LIBCPP_HAS_NO_BUILTIN_ADDRESSOF

    template <class _Tp>
    inline __WI_LIBCPP_CONSTEXPR_AFTER_CXX14
    __WI_LIBCPP_NO_CFI __WI_LIBCPP_INLINE_VISIBILITY
    _Tp*
    addressof(_Tp& __x) WI_NOEXCEPT
    {
        return __builtin_addressof(__x);
    }

#else

    template <class _Tp>
    inline __WI_LIBCPP_NO_CFI __WI_LIBCPP_INLINE_VISIBILITY
    _Tp*
    addressof(_Tp& __x) WI_NOEXCEPT
    {
    return reinterpret_cast<_Tp *>(
        const_cast<char *>(&reinterpret_cast<const volatile char &>(__x)));
    }

#endif // __WI_LIBCPP_HAS_NO_BUILTIN_ADDRESSOF

#if !defined(__WI_LIBCPP_CXX03_LANG)
    template <class _Tp> _Tp* addressof(const _Tp&&) WI_NOEXCEPT = delete;
#endif

    struct __two {char __lx[2];};

    // helper class:

    template <class _Tp, _Tp __v>
    struct __WI_LIBCPP_TEMPLATE_VIS integral_constant
    {
        static __WI_LIBCPP_CONSTEXPR const _Tp      value = __v;
        typedef _Tp               value_type;
        typedef integral_constant type;
        __WI_LIBCPP_INLINE_VISIBILITY
            __WI_LIBCPP_CONSTEXPR operator value_type() const WI_NOEXCEPT {return value;}
#if __WI_LIBCPP_STD_VER > 11
        __WI_LIBCPP_INLINE_VISIBILITY
            constexpr value_type operator ()() const WI_NOEXCEPT {return value;}
#endif
    };

    template <class _Tp, _Tp __v>
    __WI_LIBCPP_CONSTEXPR const _Tp integral_constant<_Tp, __v>::value;

#if !defined(__WI_LIBCPP_CXX03_LANG)
    template <bool __b>
    using bool_constant = integral_constant<bool, __b>;
#define __WI_LIBCPP_BOOL_CONSTANT(__b) bool_constant<(__b)>
#else
#define __WI_LIBCPP_BOOL_CONSTANT(__b) integral_constant<bool,(__b)>
#endif

    typedef __WI_LIBCPP_BOOL_CONSTANT(true)  true_type;
    typedef __WI_LIBCPP_BOOL_CONSTANT(false) false_type;

#if !defined(__WI_LIBCPP_CXX03_LANG)

    // __lazy_and

    template <bool _Last, class ..._Preds>
    struct __lazy_and_impl;

    template <class ..._Preds>
    struct __lazy_and_impl<false, _Preds...> : false_type {};

    template <>
    struct __lazy_and_impl<true> : true_type {};

    template <class _Pred>
    struct __lazy_and_impl<true, _Pred> : integral_constant<bool, _Pred::type::value> {};

    template <class _Hp, class ..._Tp>
    struct __lazy_and_impl<true, _Hp, _Tp...> : __lazy_and_impl<_Hp::type::value, _Tp...> {};

    template <class _P1, class ..._Pr>
    struct __lazy_and : __lazy_and_impl<_P1::type::value, _Pr...> {};

    // __lazy_or

    template <bool _List, class ..._Preds>
    struct __lazy_or_impl;

    template <class ..._Preds>
    struct __lazy_or_impl<true, _Preds...> : true_type {};

    template <>
    struct __lazy_or_impl<false> : false_type {};

    template <class _Hp, class ..._Tp>
    struct __lazy_or_impl<false, _Hp, _Tp...>
            : __lazy_or_impl<_Hp::type::value, _Tp...> {};

    template <class _P1, class ..._Pr>
    struct __lazy_or : __lazy_or_impl<_P1::type::value, _Pr...> {};

    // __lazy_not

    template <class _Pred>
    struct __lazy_not : integral_constant<bool, !_Pred::type::value> {};

    // __and_
    template<class...> struct __and_;
    template<> struct __and_<> : true_type {};

    template<class _B0> struct __and_<_B0> : _B0 {};

    template<class _B0, class _B1>
    struct __and_<_B0, _B1> : conditional<_B0::value, _B1, _B0>::type {};

    template<class _B0, class _B1, class _B2, class... _Bn>
    struct __and_<_B0, _B1, _B2, _Bn...>
            : conditional<_B0::value, __and_<_B1, _B2, _Bn...>, _B0>::type {};

    // __or_
    template<class...> struct __or_;
    template<> struct __or_<> : false_type {};

    template<class _B0> struct __or_<_B0> : _B0 {};

    template<class _B0, class _B1>
    struct __or_<_B0, _B1> : conditional<_B0::value, _B0, _B1>::type {};

    template<class _B0, class _B1, class _B2, class... _Bn>
    struct __or_<_B0, _B1, _B2, _Bn...>
            : conditional<_B0::value, _B0, __or_<_B1, _B2, _Bn...> >::type {};

    // __not_
    template<class _Tp>
    struct __not_ : conditional<_Tp::value, false_type, true_type>::type {};

#endif // !defined(__WI_LIBCPP_CXX03_LANG)

    // is_const

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_const            : public false_type {};
    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_const<_Tp const> : public true_type {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_const_v
        = is_const<_Tp>::value;
#endif

    // is_volatile

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_volatile               : public false_type {};
    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_volatile<_Tp volatile> : public true_type {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_volatile_v
        = is_volatile<_Tp>::value;
#endif

    // remove_const

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS remove_const            {typedef _Tp type;};
    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS remove_const<const _Tp> {typedef _Tp type;};
#if __WI_LIBCPP_STD_VER > 11
    template <class _Tp> using remove_const_t = typename remove_const<_Tp>::type;
#endif

    // remove_volatile

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS remove_volatile               {typedef _Tp type;};
    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS remove_volatile<volatile _Tp> {typedef _Tp type;};
#if __WI_LIBCPP_STD_VER > 11
    template <class _Tp> using remove_volatile_t = typename remove_volatile<_Tp>::type;
#endif

    // remove_cv

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS remove_cv
    {typedef typename remove_volatile<typename remove_const<_Tp>::type>::type type;};
#if __WI_LIBCPP_STD_VER > 11
    template <class _Tp> using remove_cv_t = typename remove_cv<_Tp>::type;
#endif

    // is_void

    template <class _Tp> struct __libcpp_is_void       : public false_type {};
    template <>          struct __libcpp_is_void<void> : public true_type {};

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_void
        : public __libcpp_is_void<typename remove_cv<_Tp>::type> {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_void_v
        = is_void<_Tp>::value;
#endif

    // __is_nullptr_t

    template <class _Tp> struct __is_nullptr_t_impl       : public false_type {};
    template <>          struct __is_nullptr_t_impl<nullptr_t> : public true_type {};

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS __is_nullptr_t
        : public __is_nullptr_t_impl<typename remove_cv<_Tp>::type> {};

#if __WI_LIBCPP_STD_VER > 11
    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_null_pointer
        : public __is_nullptr_t_impl<typename remove_cv<_Tp>::type> {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_null_pointer_v
        = is_null_pointer<_Tp>::value;
#endif
#endif

    // is_integral

    template <class _Tp> struct __libcpp_is_integral                     : public false_type {};
    template <>          struct __libcpp_is_integral<bool>               : public true_type {};
    template <>          struct __libcpp_is_integral<char>               : public true_type {};
    template <>          struct __libcpp_is_integral<signed char>        : public true_type {};
    template <>          struct __libcpp_is_integral<unsigned char>      : public true_type {};
#ifdef _MSC_VER
    template <>          struct __libcpp_is_integral<__wchar_t>          : public true_type {};
#else
    template <>          struct __libcpp_is_integral<wchar_t>            : public true_type {};
#endif
#ifndef __WI_LIBCPP_HAS_NO_UNICODE_CHARS
    template <>          struct __libcpp_is_integral<char16_t>           : public true_type {};
    template <>          struct __libcpp_is_integral<char32_t>           : public true_type {};
#endif  // __WI_LIBCPP_HAS_NO_UNICODE_CHARS
    template <>          struct __libcpp_is_integral<short>              : public true_type {};
    template <>          struct __libcpp_is_integral<unsigned short>     : public true_type {};
    template <>          struct __libcpp_is_integral<int>                : public true_type {};
    template <>          struct __libcpp_is_integral<unsigned int>       : public true_type {};
    template <>          struct __libcpp_is_integral<long>               : public true_type {};
    template <>          struct __libcpp_is_integral<unsigned long>      : public true_type {};
    template <>          struct __libcpp_is_integral<long long>          : public true_type {};
    template <>          struct __libcpp_is_integral<unsigned long long> : public true_type {};
#ifndef __WI_LIBCPP_HAS_NO_INT128
    template <>          struct __libcpp_is_integral<__int128_t>         : public true_type {};
    template <>          struct __libcpp_is_integral<__uint128_t>        : public true_type {};
#endif

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_integral
        : public __libcpp_is_integral<typename remove_cv<_Tp>::type> {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_integral_v
        = is_integral<_Tp>::value;
#endif

    // is_floating_point

    template <class _Tp> struct __libcpp_is_floating_point              : public false_type {};
    template <>          struct __libcpp_is_floating_point<float>       : public true_type {};
    template <>          struct __libcpp_is_floating_point<double>      : public true_type {};
    template <>          struct __libcpp_is_floating_point<long double> : public true_type {};

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_floating_point
        : public __libcpp_is_floating_point<typename remove_cv<_Tp>::type> {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_floating_point_v
        = is_floating_point<_Tp>::value;
#endif

    // is_array

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_array
        : public false_type {};
    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_array<_Tp[]>
        : public true_type {};
    template <class _Tp, size_t _Np> struct __WI_LIBCPP_TEMPLATE_VIS is_array<_Tp[_Np]>
        : public true_type {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_array_v
        = is_array<_Tp>::value;
#endif

    // is_pointer

    template <class _Tp> struct __libcpp_is_pointer       : public false_type {};
    template <class _Tp> struct __libcpp_is_pointer<_Tp*> : public true_type {};

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_pointer
        : public __libcpp_is_pointer<typename remove_cv<_Tp>::type> {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_pointer_v
        = is_pointer<_Tp>::value;
#endif

    // is_reference

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_lvalue_reference       : public false_type {};
    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_lvalue_reference<_Tp&> : public true_type {};

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_rvalue_reference        : public false_type {};
#ifndef __WI_LIBCPP_HAS_NO_RVALUE_REFERENCES
    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_rvalue_reference<_Tp&&> : public true_type {};
#endif

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_reference        : public false_type {};
    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_reference<_Tp&>  : public true_type {};
#ifndef __WI_LIBCPP_HAS_NO_RVALUE_REFERENCES
    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_reference<_Tp&&> : public true_type {};
#endif

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_reference_v
        = is_reference<_Tp>::value;

    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_lvalue_reference_v
        = is_lvalue_reference<_Tp>::value;

    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_rvalue_reference_v
        = is_rvalue_reference<_Tp>::value;
#endif
    // is_union

#if __WI_HAS_FEATURE_IS_UNION || (__WI_GNUC_VER >= 403)

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_union
        : public integral_constant<bool, __is_union(_Tp)> {};

#else

    template <class _Tp> struct __libcpp_union : public false_type {};
    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_union
        : public __libcpp_union<typename remove_cv<_Tp>::type> {};

#endif

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_union_v
        = is_union<_Tp>::value;
#endif

    // is_class

#if __WI_HAS_FEATURE_IS_CLASS || (__WI_GNUC_VER >= 403)

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_class
        : public integral_constant<bool, __is_class(_Tp)> {};

#else

    namespace __is_class_imp
    {
    template <class _Tp> char  __test(int _Tp::*);
    template <class _Tp> __two __test(...);
    }

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_class
        : public integral_constant<bool, sizeof(__is_class_imp::__test<_Tp>(0)) == 1 && !is_union<_Tp>::value> {};

#endif

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_class_v
        = is_class<_Tp>::value;
#endif

    // is_same

    template <class _Tp, class _Up> struct __WI_LIBCPP_TEMPLATE_VIS is_same           : public false_type {};
    template <class _Tp>            struct __WI_LIBCPP_TEMPLATE_VIS is_same<_Tp, _Tp> : public true_type {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp, class _Up>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_same_v
        = is_same<_Tp, _Up>::value;
#endif

    // is_function

    namespace __libcpp_is_function_imp
    {
    struct __dummy_type {};
    template <class _Tp> char  __test(_Tp*);
    template <class _Tp> char __test(__dummy_type);
    template <class _Tp> __two __test(...);
    template <class _Tp> _Tp&  __source(int);
    template <class _Tp> __dummy_type __source(...);
    }

    template <class _Tp, bool = is_class<_Tp>::value ||
                                is_union<_Tp>::value ||
                                is_void<_Tp>::value  ||
                                is_reference<_Tp>::value ||
                                __is_nullptr_t<_Tp>::value >
    struct __libcpp_is_function
        : public integral_constant<bool, sizeof(__libcpp_is_function_imp::__test<_Tp>(__libcpp_is_function_imp::__source<_Tp>(0))) == 1>
        {};
    template <class _Tp> struct __libcpp_is_function<_Tp, true> : public false_type {};

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_function
        : public __libcpp_is_function<_Tp> {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_function_v
        = is_function<_Tp>::value;
#endif

    // is_member_function_pointer

    // template <class _Tp> struct            __libcpp_is_member_function_pointer             : public false_type {};
    // template <class _Tp, class _Up> struct __libcpp_is_member_function_pointer<_Tp _Up::*> : public is_function<_Tp> {};
    //

    template <class _Mp, bool _IsMemberFunctionPtr, bool _IsMemberObjectPtr>
    struct __member_pointer_traits_imp
    {  // forward declaration; specializations later
    };


    template <class _Tp> struct __libcpp_is_member_function_pointer
        : public false_type {};

    template <class _Ret, class _Class>
    struct __libcpp_is_member_function_pointer<_Ret _Class::*>
        : public is_function<_Ret> {};

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_member_function_pointer
        : public __libcpp_is_member_function_pointer<typename remove_cv<_Tp>::type>::type {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_member_function_pointer_v
        = is_member_function_pointer<_Tp>::value;
#endif

    // is_member_pointer

    template <class _Tp>            struct __libcpp_is_member_pointer             : public false_type {};
    template <class _Tp, class _Up> struct __libcpp_is_member_pointer<_Tp _Up::*> : public true_type {};

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_member_pointer
        : public __libcpp_is_member_pointer<typename remove_cv<_Tp>::type> {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_member_pointer_v
        = is_member_pointer<_Tp>::value;
#endif

    // is_member_object_pointer

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_member_object_pointer
        : public integral_constant<bool, is_member_pointer<_Tp>::value &&
                                        !is_member_function_pointer<_Tp>::value> {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_member_object_pointer_v
        = is_member_object_pointer<_Tp>::value;
#endif

    // is_enum

#if __WI_HAS_FEATURE_IS_ENUM || (__WI_GNUC_VER >= 403)

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_enum
        : public integral_constant<bool, __is_enum(_Tp)> {};

#else

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_enum
        : public integral_constant<bool, !is_void<_Tp>::value             &&
                                        !is_integral<_Tp>::value         &&
                                        !is_floating_point<_Tp>::value   &&
                                        !is_array<_Tp>::value            &&
                                        !is_pointer<_Tp>::value          &&
                                        !is_reference<_Tp>::value        &&
                                        !is_member_pointer<_Tp>::value   &&
                                        !is_union<_Tp>::value            &&
                                        !is_class<_Tp>::value            &&
                                        !is_function<_Tp>::value         > {};

#endif

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_enum_v
        = is_enum<_Tp>::value;
#endif

    // is_arithmetic

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_arithmetic
        : public integral_constant<bool, is_integral<_Tp>::value      ||
                                        is_floating_point<_Tp>::value> {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_arithmetic_v
        = is_arithmetic<_Tp>::value;
#endif

    // is_fundamental

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_fundamental
        : public integral_constant<bool, is_void<_Tp>::value        ||
                                        __is_nullptr_t<_Tp>::value ||
                                        is_arithmetic<_Tp>::value> {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_fundamental_v
        = is_fundamental<_Tp>::value;
#endif

    // is_scalar

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_scalar
        : public integral_constant<bool, is_arithmetic<_Tp>::value     ||
                                        is_member_pointer<_Tp>::value ||
                                        is_pointer<_Tp>::value        ||
                                        __is_nullptr_t<_Tp>::value    ||
                                        is_enum<_Tp>::value           > {};

    template <> struct __WI_LIBCPP_TEMPLATE_VIS is_scalar<nullptr_t> : public true_type {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_scalar_v
        = is_scalar<_Tp>::value;
#endif

    // is_object

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_object
        : public integral_constant<bool, is_scalar<_Tp>::value ||
                                        is_array<_Tp>::value  ||
                                        is_union<_Tp>::value  ||
                                        is_class<_Tp>::value  > {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_object_v
        = is_object<_Tp>::value;
#endif

    // is_compound

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_compound
        : public integral_constant<bool, !is_fundamental<_Tp>::value> {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_compound_v
        = is_compound<_Tp>::value;
#endif


    // __is_referenceable  [defns.referenceable]

    struct __is_referenceable_impl {
        template <class _Tp> static _Tp& __test(int);
        template <class _Tp> static __two __test(...);
    };

    template <class _Tp>
    struct __is_referenceable : integral_constant<bool,
        !is_same<decltype(__is_referenceable_impl::__test<_Tp>(0)), __two>::value> {};


    // add_const

    template <class _Tp, bool = is_reference<_Tp>::value ||
                                is_function<_Tp>::value  ||
                                is_const<_Tp>::value     >
    struct __add_const             {typedef _Tp type;};

    template <class _Tp>
    struct __add_const<_Tp, false> {typedef const _Tp type;};

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS add_const
        {typedef typename __add_const<_Tp>::type type;};

#if __WI_LIBCPP_STD_VER > 11
    template <class _Tp> using add_const_t = typename add_const<_Tp>::type;
#endif

    // add_volatile

    template <class _Tp, bool = is_reference<_Tp>::value ||
                                is_function<_Tp>::value  ||
                                is_volatile<_Tp>::value  >
    struct __add_volatile             {typedef _Tp type;};

    template <class _Tp>
    struct __add_volatile<_Tp, false> {typedef volatile _Tp type;};

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS add_volatile
        {typedef typename __add_volatile<_Tp>::type type;};

#if __WI_LIBCPP_STD_VER > 11
    template <class _Tp> using add_volatile_t = typename add_volatile<_Tp>::type;
#endif

    // add_cv

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS add_cv
        {typedef typename add_const<typename add_volatile<_Tp>::type>::type type;};

#if __WI_LIBCPP_STD_VER > 11
    template <class _Tp> using add_cv_t = typename add_cv<_Tp>::type;
#endif

    // remove_reference

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS remove_reference        {typedef _Tp type;};
    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS remove_reference<_Tp&>  {typedef _Tp type;};
#ifndef __WI_LIBCPP_HAS_NO_RVALUE_REFERENCES
    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS remove_reference<_Tp&&> {typedef _Tp type;};
#endif

#if __WI_LIBCPP_STD_VER > 11
    template <class _Tp> using remove_reference_t = typename remove_reference<_Tp>::type;
#endif

    // add_lvalue_reference

    template <class _Tp, bool = __is_referenceable<_Tp>::value> struct __add_lvalue_reference_impl            { typedef _Tp  type; };
    template <class _Tp                                       > struct __add_lvalue_reference_impl<_Tp, true> { typedef _Tp& type; };

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS add_lvalue_reference
    {typedef typename __add_lvalue_reference_impl<_Tp>::type type;};

#if __WI_LIBCPP_STD_VER > 11
    template <class _Tp> using add_lvalue_reference_t = typename add_lvalue_reference<_Tp>::type;
#endif

#ifndef __WI_LIBCPP_HAS_NO_RVALUE_REFERENCES

    template <class _Tp, bool = __is_referenceable<_Tp>::value> struct __add_rvalue_reference_impl            { typedef _Tp   type; };
    template <class _Tp                                       > struct __add_rvalue_reference_impl<_Tp, true> { typedef _Tp&& type; };

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS add_rvalue_reference
    {typedef typename __add_rvalue_reference_impl<_Tp>::type type;};

#if __WI_LIBCPP_STD_VER > 11
    template <class _Tp> using add_rvalue_reference_t = typename add_rvalue_reference<_Tp>::type;
#endif

#endif  // __WI_LIBCPP_HAS_NO_RVALUE_REFERENCES

#ifndef __WI_LIBCPP_HAS_NO_RVALUE_REFERENCES

    // MSVC has issues compiling some source code that uses the libc++ definition of 'declval'
#ifdef _MSC_VER
    template <typename _Tp>
    typename add_rvalue_reference<_Tp>::type declval() WI_NOEXCEPT;
#else
    template <class _Tp> _Tp&& __declval(int);
    template <class _Tp> _Tp   __declval(long);

    template <class _Tp>
    decltype(__declval<_Tp>(0))
    declval() WI_NOEXCEPT;
#endif

#else  // __WI_LIBCPP_HAS_NO_RVALUE_REFERENCES

    template <class _Tp>
    typename add_lvalue_reference<_Tp>::type
    declval();

#endif  // __WI_LIBCPP_HAS_NO_RVALUE_REFERENCES

    // __uncvref

    template <class _Tp>
    struct __uncvref  {
        typedef typename remove_cv<typename remove_reference<_Tp>::type>::type type;
    };

    template <class _Tp>
    struct __unconstref {
        typedef typename remove_const<typename remove_reference<_Tp>::type>::type type;
    };

#ifndef __WI_LIBCPP_CXX03_LANG
    template <class _Tp>
    using __uncvref_t = typename __uncvref<_Tp>::type;
#endif

    // __is_same_uncvref

    template <class _Tp, class _Up>
    struct __is_same_uncvref : is_same<typename __uncvref<_Tp>::type,
                                    typename __uncvref<_Up>::type> {};

#if __WI_LIBCPP_STD_VER > 17
    // remove_cvref - same as __uncvref
    template <class _Tp>
    struct remove_cvref : public __uncvref<_Tp> {};

    template <class _Tp> using remove_cvref_t = typename remove_cvref<_Tp>::type;
#endif


    struct __any
    {
        __any(...);
    };

    // remove_pointer

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS remove_pointer                      {typedef _Tp type;};
    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS remove_pointer<_Tp*>                {typedef _Tp type;};
    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS remove_pointer<_Tp* const>          {typedef _Tp type;};
    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS remove_pointer<_Tp* volatile>       {typedef _Tp type;};
    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS remove_pointer<_Tp* const volatile> {typedef _Tp type;};

#if __WI_LIBCPP_STD_VER > 11
    template <class _Tp> using remove_pointer_t = typename remove_pointer<_Tp>::type;
#endif

    // add_pointer

    template <class _Tp,
            bool = __is_referenceable<_Tp>::value ||
                    is_same<typename remove_cv<_Tp>::type, void>::value>
    struct __add_pointer_impl
        {typedef typename remove_reference<_Tp>::type* type;};
    template <class _Tp> struct __add_pointer_impl<_Tp, false>
        {typedef _Tp type;};

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS add_pointer
        {typedef typename __add_pointer_impl<_Tp>::type type;};

#if __WI_LIBCPP_STD_VER > 11
    template <class _Tp> using add_pointer_t = typename add_pointer<_Tp>::type;
#endif

    // type_identity
#if __WI_LIBCPP_STD_VER > 17
    template<class _Tp> struct type_identity { typedef _Tp type; };
    template<class _Tp> using type_identity_t = typename type_identity<_Tp>::type;
#endif

    // is_signed

    template <class _Tp, bool = is_integral<_Tp>::value>
    struct __libcpp_is_signed_impl : public __WI_LIBCPP_BOOL_CONSTANT(_Tp(-1) < _Tp(0)) {};

    template <class _Tp>
    struct __libcpp_is_signed_impl<_Tp, false> : public true_type {};  // floating point

    template <class _Tp, bool = is_arithmetic<_Tp>::value>
    struct __libcpp_is_signed : public __libcpp_is_signed_impl<_Tp> {};

    template <class _Tp> struct __libcpp_is_signed<_Tp, false> : public false_type {};

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_signed : public __libcpp_is_signed<_Tp> {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_signed_v
        = is_signed<_Tp>::value;
#endif

    // is_unsigned

    template <class _Tp, bool = is_integral<_Tp>::value>
    struct __libcpp_is_unsigned_impl : public __WI_LIBCPP_BOOL_CONSTANT(_Tp(0) < _Tp(-1)) {};

    template <class _Tp>
    struct __libcpp_is_unsigned_impl<_Tp, false> : public false_type {};  // floating point

    template <class _Tp, bool = is_arithmetic<_Tp>::value>
    struct __libcpp_is_unsigned : public __libcpp_is_unsigned_impl<_Tp> {};

    template <class _Tp> struct __libcpp_is_unsigned<_Tp, false> : public false_type {};

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_unsigned : public __libcpp_is_unsigned<_Tp> {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_unsigned_v
        = is_unsigned<_Tp>::value;
#endif

    // rank

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS rank
        : public integral_constant<size_t, 0> {};
    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS rank<_Tp[]>
        : public integral_constant<size_t, rank<_Tp>::value + 1> {};
    template <class _Tp, size_t _Np> struct __WI_LIBCPP_TEMPLATE_VIS rank<_Tp[_Np]>
        : public integral_constant<size_t, rank<_Tp>::value + 1> {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR size_t rank_v
        = rank<_Tp>::value;
#endif

    // extent

    template <class _Tp, unsigned _Ip = 0> struct __WI_LIBCPP_TEMPLATE_VIS extent
        : public integral_constant<size_t, 0> {};
    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS extent<_Tp[], 0>
        : public integral_constant<size_t, 0> {};
    template <class _Tp, unsigned _Ip> struct __WI_LIBCPP_TEMPLATE_VIS extent<_Tp[], _Ip>
        : public integral_constant<size_t, extent<_Tp, _Ip-1>::value> {};
    template <class _Tp, size_t _Np> struct __WI_LIBCPP_TEMPLATE_VIS extent<_Tp[_Np], 0>
        : public integral_constant<size_t, _Np> {};
    template <class _Tp, size_t _Np, unsigned _Ip> struct __WI_LIBCPP_TEMPLATE_VIS extent<_Tp[_Np], _Ip>
        : public integral_constant<size_t, extent<_Tp, _Ip-1>::value> {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp, unsigned _Ip = 0>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR size_t extent_v
        = extent<_Tp, _Ip>::value;
#endif

    // remove_extent

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS remove_extent
        {typedef _Tp type;};
    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS remove_extent<_Tp[]>
        {typedef _Tp type;};
    template <class _Tp, size_t _Np> struct __WI_LIBCPP_TEMPLATE_VIS remove_extent<_Tp[_Np]>
        {typedef _Tp type;};

#if __WI_LIBCPP_STD_VER > 11
    template <class _Tp> using remove_extent_t = typename remove_extent<_Tp>::type;
#endif

    // remove_all_extents

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS remove_all_extents
        {typedef _Tp type;};
    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS remove_all_extents<_Tp[]>
        {typedef typename remove_all_extents<_Tp>::type type;};
    template <class _Tp, size_t _Np> struct __WI_LIBCPP_TEMPLATE_VIS remove_all_extents<_Tp[_Np]>
        {typedef typename remove_all_extents<_Tp>::type type;};

#if __WI_LIBCPP_STD_VER > 11
    template <class _Tp> using remove_all_extents_t = typename remove_all_extents<_Tp>::type;
#endif

    // decay

    template <class _Up, bool>
    struct __decay {
        typedef typename remove_cv<_Up>::type type;
    };

    template <class _Up>
    struct __decay<_Up, true> {
    public:
        typedef typename conditional
                        <
                            is_array<_Up>::value,
                            typename remove_extent<_Up>::type*,
                            typename conditional
                            <
                                is_function<_Up>::value,
                                typename add_pointer<_Up>::type,
                                typename remove_cv<_Up>::type
                            >::type
                        >::type type;
    };

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS decay
    {
    private:
        typedef typename remove_reference<_Tp>::type _Up;
    public:
        typedef typename __decay<_Up, __is_referenceable<_Up>::value>::type type;
    };

#if __WI_LIBCPP_STD_VER > 11
    template <class _Tp> using decay_t = typename decay<_Tp>::type;
#endif

    // is_abstract

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_abstract
        : public integral_constant<bool, __is_abstract(_Tp)> {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_abstract_v
        = is_abstract<_Tp>::value;
#endif

    // is_final

#if defined(__WI_LIBCPP_HAS_IS_FINAL)
    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS
    __libcpp_is_final : public integral_constant<bool, __is_final(_Tp)> {};
#else
    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS
    __libcpp_is_final : public false_type {};
#endif

#if defined(__WI_LIBCPP_HAS_IS_FINAL) && __WI_LIBCPP_STD_VER > 11
    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS
    is_final : public integral_constant<bool, __is_final(_Tp)> {};
#endif

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_final_v
        = is_final<_Tp>::value;
#endif

    // is_aggregate
#if __WI_LIBCPP_STD_VER > 14 && !defined(__WI_LIBCPP_HAS_NO_IS_AGGREGATE)

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS
    is_aggregate : public integral_constant<bool, __is_aggregate(_Tp)> {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR constexpr bool is_aggregate_v
        = is_aggregate<_Tp>::value;
#endif

#endif // __WI_LIBCPP_STD_VER > 14 && !defined(__WI_LIBCPP_HAS_NO_IS_AGGREGATE)

    // is_base_of

#ifdef __WI_LIBCPP_HAS_IS_BASE_OF

    template <class _Bp, class _Dp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_base_of
        : public integral_constant<bool, __is_base_of(_Bp, _Dp)> {};

#else  // __WI_LIBCPP_HAS_IS_BASE_OF

    namespace __is_base_of_imp
    {
    template <class _Tp>
    struct _Dst
    {
        _Dst(const volatile _Tp &);
    };
    template <class _Tp>
    struct _Src
    {
        operator const volatile _Tp &();
        template <class _Up> operator const _Dst<_Up> &();
    };
    template <size_t> struct __one { typedef char type; };
    template <class _Bp, class _Dp> typename __one<sizeof(_Dst<_Bp>(declval<_Src<_Dp> >()))>::type __test(int);
    template <class _Bp, class _Dp> __two __test(...);
    }

    template <class _Bp, class _Dp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_base_of
        : public integral_constant<bool, is_class<_Bp>::value &&
                                        sizeof(__is_base_of_imp::__test<_Bp, _Dp>(0)) == 2> {};

#endif  // __WI_LIBCPP_HAS_IS_BASE_OF

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Bp, class _Dp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_base_of_v
        = is_base_of<_Bp, _Dp>::value;
#endif

    // is_convertible

#if __WI_HAS_FEATURE_IS_CONVERTIBLE_TO && !defined(__WI_LIBCPP_USE_IS_CONVERTIBLE_FALLBACK)

    template <class _T1, class _T2> struct __WI_LIBCPP_TEMPLATE_VIS is_convertible
        : public integral_constant<bool, __is_convertible_to(_T1, _T2) &&
                                        !is_abstract<_T2>::value> {};

#else  // __WI_HAS_FEATURE_IS_CONVERTIBLE_TO

    namespace __is_convertible_imp
    {
    template <class _Tp> void  __test_convert(_Tp);

    template <class _From, class _To, class = void>
    struct __is_convertible_test : public false_type {};

    template <class _From, class _To>
    struct __is_convertible_test<_From, _To,
        decltype(__is_convertible_imp::__test_convert<_To>(declval<_From>()))> : public true_type
    {};

    template <class _Tp, bool _IsArray =    is_array<_Tp>::value,
                        bool _IsFunction = is_function<_Tp>::value,
                        bool _IsVoid =     is_void<_Tp>::value>
                        struct __is_array_function_or_void                          {enum {value = 0};};
    template <class _Tp> struct __is_array_function_or_void<_Tp, true, false, false> {enum {value = 1};};
    template <class _Tp> struct __is_array_function_or_void<_Tp, false, true, false> {enum {value = 2};};
    template <class _Tp> struct __is_array_function_or_void<_Tp, false, false, true> {enum {value = 3};};
    }

    template <class _Tp,
        unsigned = __is_convertible_imp::__is_array_function_or_void<typename remove_reference<_Tp>::type>::value>
    struct __is_convertible_check
    {
        static const size_t __v = 0;
    };

    template <class _Tp>
    struct __is_convertible_check<_Tp, 0>
    {
        static const size_t __v = sizeof(_Tp);
    };

    template <class _T1, class _T2,
        unsigned _T1_is_array_function_or_void = __is_convertible_imp::__is_array_function_or_void<_T1>::value,
        unsigned _T2_is_array_function_or_void = __is_convertible_imp::__is_array_function_or_void<_T2>::value>
    struct __is_convertible
        : public integral_constant<bool,
            __is_convertible_imp::__is_convertible_test<_T1, _T2>::value
#if defined(__WI_LIBCPP_HAS_NO_RVALUE_REFERENCES)
            && !(!is_function<_T1>::value && !is_reference<_T1>::value && is_reference<_T2>::value
                && (!is_const<typename remove_reference<_T2>::type>::value
                    || is_volatile<typename remove_reference<_T2>::type>::value)
                    && (is_same<typename remove_cv<_T1>::type,
                                typename remove_cv<typename remove_reference<_T2>::type>::type>::value
                        || is_base_of<typename remove_reference<_T2>::type, _T1>::value))
#endif
        >
    {};

    template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 0, 1> : public false_type {};
    template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 1, 1> : public false_type {};
    template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 2, 1> : public false_type {};
    template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 3, 1> : public false_type {};

    template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 0, 2> : public false_type {};
    template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 1, 2> : public false_type {};
    template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 2, 2> : public false_type {};
    template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 3, 2> : public false_type {};

    template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 0, 3> : public false_type {};
    template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 1, 3> : public false_type {};
    template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 2, 3> : public false_type {};
    template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 3, 3> : public true_type {};

    template <class _T1, class _T2> struct __WI_LIBCPP_TEMPLATE_VIS is_convertible
        : public __is_convertible<_T1, _T2>
    {
        static const size_t __complete_check1 = __is_convertible_check<_T1>::__v;
        static const size_t __complete_check2 = __is_convertible_check<_T2>::__v;
    };

#endif  // __WI_HAS_FEATURE_IS_CONVERTIBLE_TO

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _From, class _To>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_convertible_v
        = is_convertible<_From, _To>::value;
#endif

    // is_empty

#if __WI_HAS_FEATURE_IS_EMPTY || (__WI_GNUC_VER >= 407)

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_empty
        : public integral_constant<bool, __is_empty(_Tp)> {};

#else  // __WI_HAS_FEATURE_IS_EMPTY

    template <class _Tp>
    struct __is_empty1
        : public _Tp
    {
        double __lx;
    };

    struct __is_empty2
    {
        double __lx;
    };

    template <class _Tp, bool = is_class<_Tp>::value>
    struct __libcpp_empty : public integral_constant<bool, sizeof(__is_empty1<_Tp>) == sizeof(__is_empty2)> {};

    template <class _Tp> struct __libcpp_empty<_Tp, false> : public false_type {};

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_empty : public __libcpp_empty<_Tp> {};

#endif  // __WI_HAS_FEATURE_IS_EMPTY

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_empty_v
        = is_empty<_Tp>::value;
#endif

    // is_polymorphic

#if __WI_HAS_FEATURE_IS_POLYMORPHIC

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_polymorphic
        : public integral_constant<bool, __is_polymorphic(_Tp)> {};

#else

    template<typename _Tp> char &__is_polymorphic_impl(
        typename enable_if<sizeof((_Tp*)dynamic_cast<const volatile void*>(declval<_Tp*>())) != 0,
                        int>::type);
    template<typename _Tp> __two &__is_polymorphic_impl(...);

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_polymorphic
        : public integral_constant<bool, sizeof(__is_polymorphic_impl<_Tp>(0)) == 1> {};

#endif // __WI_HAS_FEATURE_IS_POLYMORPHIC

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_polymorphic_v
        = is_polymorphic<_Tp>::value;
#endif

    // has_virtual_destructor

#if __WI_HAS_FEATURE_HAS_VIRTUAL_DESTRUCTOR || (__WI_GNUC_VER >= 403)

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS has_virtual_destructor
        : public integral_constant<bool, __has_virtual_destructor(_Tp)> {};

#else

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS has_virtual_destructor
        : public false_type {};

#endif

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool has_virtual_destructor_v
        = has_virtual_destructor<_Tp>::value;
#endif

    // has_unique_object_representations

#if __WI_LIBCPP_STD_VER > 14 && defined(__WI_LIBCPP_HAS_UNIQUE_OBJECT_REPRESENTATIONS)

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS has_unique_object_representations
        : public integral_constant<bool,
        __has_unique_object_representations(remove_cv_t<remove_all_extents_t<_Tp>>)> {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool has_unique_object_representations_v
        = has_unique_object_representations<_Tp>::value;
#endif

#endif

    // alignment_of

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS alignment_of
        : public integral_constant<size_t, __alignof__(_Tp)> {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR size_t alignment_of_v
        = alignment_of<_Tp>::value;
#endif

    // aligned_storage

    template <class _Hp, class _Tp>
    struct __type_list
    {
        typedef _Hp _Head;
        typedef _Tp _Tail;
    };

    struct __nat
    {
#ifndef __WI_LIBCPP_CXX03_LANG
        __nat() = delete;
        __nat(const __nat&) = delete;
        __nat& operator=(const __nat&) = delete;
        ~__nat() = delete;
#endif
    };

    template <class _Tp>
    struct __align_type
    {
        static const size_t value = alignment_of<_Tp>::value;
        typedef _Tp type;
    };

    struct __struct_double {long double __lx;};
    struct __struct_double4 {double __lx[4];};

    typedef
        __type_list<__align_type<unsigned char>,
        __type_list<__align_type<unsigned short>,
        __type_list<__align_type<unsigned int>,
        __type_list<__align_type<unsigned long>,
        __type_list<__align_type<unsigned long long>,
        __type_list<__align_type<double>,
        __type_list<__align_type<long double>,
        __type_list<__align_type<__struct_double>,
        __type_list<__align_type<__struct_double4>,
        __type_list<__align_type<int*>,
        __nat
        > > > > > > > > > > __all_types;

    template <class _TL, size_t _Align> struct __find_pod;

    template <class _Hp, size_t _Align>
    struct __find_pod<__type_list<_Hp, __nat>, _Align>
    {
        typedef typename conditional<
                                _Align == _Hp::value,
                                typename _Hp::type,
                                void
                            >::type type;
    };

    template <class _Hp, class _Tp, size_t _Align>
    struct __find_pod<__type_list<_Hp, _Tp>, _Align>
    {
        typedef typename conditional<
                                _Align == _Hp::value,
                                typename _Hp::type,
                                typename __find_pod<_Tp, _Align>::type
                            >::type type;
    };

    template <size_t _Align>
    struct __has_pod_with_align : public integral_constant<bool, !is_same<typename __find_pod<__all_types, _Align>::type, void>::value> {};

    template <class _TL, size_t _Len> struct __find_max_align;

    template <class _Hp, size_t _Len>
    struct __find_max_align<__type_list<_Hp, __nat>, _Len> : public integral_constant<size_t, _Hp::value> {};

    template <size_t _Len, size_t _A1, size_t _A2>
    struct __select_align
    {
    private:
        static const size_t __min = _A2 < _A1 ? _A2 : _A1;
        static const size_t __max = _A1 < _A2 ? _A2 : _A1;
    public:
        static const size_t value = _Len < __max ? __min : __max;
    };

    template <class _Hp, class _Tp, size_t _Len>
    struct __find_max_align<__type_list<_Hp, _Tp>, _Len>
        : public integral_constant<size_t, __select_align<_Len, _Hp::value, __find_max_align<_Tp, _Len>::value>::value> {};

    template <size_t _Len, size_t _Align, bool = __has_pod_with_align<_Align>::value>
    struct __aligned_storage
    {
        typedef typename __find_pod<__all_types, _Align>::type _Aligner;
        static_assert(!is_void<_Aligner>::value, "");
        union type
        {
            _Aligner __align;
            unsigned char __data[(_Len + _Align - 1)/_Align * _Align];
        };
    };

#define __WI_CREATE_ALIGNED_STORAGE_SPECIALIZATION(n) \
    template <size_t _Len>\
    struct __aligned_storage<_Len, n, false>\
    {\
        struct __WI_ALIGNAS(n) type\
        {\
            unsigned char __lx[(_Len + n - 1)/n * n];\
        };\
    }

    __WI_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x1);
    __WI_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x2);
    __WI_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x4);
    __WI_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x8);
    __WI_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x10);
    __WI_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x20);
    __WI_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x40);
    __WI_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x80);
    __WI_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x100);
    __WI_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x200);
    __WI_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x400);
    __WI_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x800);
    __WI_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x1000);
    __WI_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x2000);
    // PE/COFF does not support alignment beyond 8192 (=0x2000)
#if !defined(__WI_LIBCPP_OBJECT_FORMAT_COFF)
    __WI_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x4000);
#endif // !defined(__WI_LIBCPP_OBJECT_FORMAT_COFF)

#undef __WI_CREATE_ALIGNED_STORAGE_SPECIALIZATION

    template <size_t _Len, size_t _Align = __find_max_align<__all_types, _Len>::value>
    struct __WI_LIBCPP_TEMPLATE_VIS aligned_storage : public __aligned_storage<_Len, _Align> {};

#if __WI_LIBCPP_STD_VER > 11
    template <size_t _Len, size_t _Align = __find_max_align<__all_types, _Len>::value>
        using aligned_storage_t = typename aligned_storage<_Len, _Align>::type;
#endif

#ifndef __WI_LIBCPP_HAS_NO_VARIADICS

    // aligned_union

    template <size_t _I0, size_t ..._In>
    struct __static_max;

    template <size_t _I0>
    struct __static_max<_I0>
    {
        static const size_t value = _I0;
    };

    template <size_t _I0, size_t _I1, size_t ..._In>
    struct __static_max<_I0, _I1, _In...>
    {
        static const size_t value = _I0 >= _I1 ? __static_max<_I0, _In...>::value :
                                                __static_max<_I1, _In...>::value;
    };

    template <size_t _Len, class _Type0, class ..._Types>
    struct aligned_union
    {
        static const size_t alignment_value = __static_max<__alignof__(_Type0),
                                                        __alignof__(_Types)...>::value;
        static const size_t __len = __static_max<_Len, sizeof(_Type0),
                                                sizeof(_Types)...>::value;
        typedef typename aligned_storage<__len, alignment_value>::type type;
    };

#if __WI_LIBCPP_STD_VER > 11
    template <size_t _Len, class ..._Types> using aligned_union_t = typename aligned_union<_Len, _Types...>::type;
#endif

#endif  // __WI_LIBCPP_HAS_NO_VARIADICS

    template <class _Tp>
    struct __numeric_type
    {
    static void __test(...);
    static float __test(float);
    static double __test(char);
    static double __test(int);
    static double __test(unsigned);
    static double __test(long);
    static double __test(unsigned long);
    static double __test(long long);
    static double __test(unsigned long long);
    static double __test(double);
    static long double __test(long double);

    typedef decltype(__test(declval<_Tp>())) type;
    static const bool value = !is_same<type, void>::value;
    };

    template <>
    struct __numeric_type<void>
    {
    static const bool value = true;
    };

    // __promote

    template <class _A1, class _A2 = void, class _A3 = void,
            bool = __numeric_type<_A1>::value &&
                    __numeric_type<_A2>::value &&
                    __numeric_type<_A3>::value>
    class __promote_imp
    {
    public:
        static const bool value = false;
    };

    template <class _A1, class _A2, class _A3>
    class __promote_imp<_A1, _A2, _A3, true>
    {
    private:
        typedef typename __promote_imp<_A1>::type __type1;
        typedef typename __promote_imp<_A2>::type __type2;
        typedef typename __promote_imp<_A3>::type __type3;
    public:
        typedef decltype(__type1() + __type2() + __type3()) type;
        static const bool value = true;
    };

    template <class _A1, class _A2>
    class __promote_imp<_A1, _A2, void, true>
    {
    private:
        typedef typename __promote_imp<_A1>::type __type1;
        typedef typename __promote_imp<_A2>::type __type2;
    public:
        typedef decltype(__type1() + __type2()) type;
        static const bool value = true;
    };

    template <class _A1>
    class __promote_imp<_A1, void, void, true>
    {
    public:
        typedef typename __numeric_type<_A1>::type type;
        static const bool value = true;
    };

    template <class _A1, class _A2 = void, class _A3 = void>
    class __promote : public __promote_imp<_A1, _A2, _A3> {};

    // make_signed / make_unsigned

    typedef
        __type_list<signed char,
        __type_list<signed short,
        __type_list<signed int,
        __type_list<signed long,
        __type_list<signed long long,
#ifndef __WI_LIBCPP_HAS_NO_INT128
        __type_list<__int128_t,
#endif
        __nat
#ifndef __WI_LIBCPP_HAS_NO_INT128
        >
#endif
        > > > > > __signed_types;

    typedef
        __type_list<unsigned char,
        __type_list<unsigned short,
        __type_list<unsigned int,
        __type_list<unsigned long,
        __type_list<unsigned long long,
#ifndef __WI_LIBCPP_HAS_NO_INT128
        __type_list<__uint128_t,
#endif
        __nat
#ifndef __WI_LIBCPP_HAS_NO_INT128
        >
#endif
        > > > > > __unsigned_types;

    template <class _TypeList, size_t _Size, bool = _Size <= sizeof(typename _TypeList::_Head)> struct __find_first;

    template <class _Hp, class _Tp, size_t _Size>
    struct __find_first<__type_list<_Hp, _Tp>, _Size, true>
    {
        typedef _Hp type;
    };

    template <class _Hp, class _Tp, size_t _Size>
    struct __find_first<__type_list<_Hp, _Tp>, _Size, false>
    {
        typedef typename __find_first<_Tp, _Size>::type type;
    };

    template <class _Tp, class _Up, bool = is_const<typename remove_reference<_Tp>::type>::value,
                                bool = is_volatile<typename remove_reference<_Tp>::type>::value>
    struct __apply_cv
    {
        typedef _Up type;
    };

    template <class _Tp, class _Up>
    struct __apply_cv<_Tp, _Up, true, false>
    {
        typedef const _Up type;
    };

    template <class _Tp, class _Up>
    struct __apply_cv<_Tp, _Up, false, true>
    {
        typedef volatile _Up type;
    };

    template <class _Tp, class _Up>
    struct __apply_cv<_Tp, _Up, true, true>
    {
        typedef const volatile _Up type;
    };

    template <class _Tp, class _Up>
    struct __apply_cv<_Tp&, _Up, false, false>
    {
        typedef _Up& type;
    };

    template <class _Tp, class _Up>
    struct __apply_cv<_Tp&, _Up, true, false>
    {
        typedef const _Up& type;
    };

    template <class _Tp, class _Up>
    struct __apply_cv<_Tp&, _Up, false, true>
    {
        typedef volatile _Up& type;
    };

    template <class _Tp, class _Up>
    struct __apply_cv<_Tp&, _Up, true, true>
    {
        typedef const volatile _Up& type;
    };

    template <class _Tp, bool = is_integral<_Tp>::value || is_enum<_Tp>::value>
    struct __make_signed {};

    template <class _Tp>
    struct __make_signed<_Tp, true>
    {
        typedef typename __find_first<__signed_types, sizeof(_Tp)>::type type;
    };

    template <> struct __make_signed<bool,               true> {};
    template <> struct __make_signed<  signed short,     true> {typedef short     type;};
    template <> struct __make_signed<unsigned short,     true> {typedef short     type;};
    template <> struct __make_signed<  signed int,       true> {typedef int       type;};
    template <> struct __make_signed<unsigned int,       true> {typedef int       type;};
    template <> struct __make_signed<  signed long,      true> {typedef long      type;};
    template <> struct __make_signed<unsigned long,      true> {typedef long      type;};
    template <> struct __make_signed<  signed long long, true> {typedef long long type;};
    template <> struct __make_signed<unsigned long long, true> {typedef long long type;};
#ifndef __WI_LIBCPP_HAS_NO_INT128
    template <> struct __make_signed<__int128_t,         true> {typedef __int128_t type;};
    template <> struct __make_signed<__uint128_t,        true> {typedef __int128_t type;};
#endif

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS make_signed
    {
        typedef typename __apply_cv<_Tp, typename __make_signed<typename remove_cv<_Tp>::type>::type>::type type;
    };

#if __WI_LIBCPP_STD_VER > 11
    template <class _Tp> using make_signed_t = typename make_signed<_Tp>::type;
#endif

    template <class _Tp, bool = is_integral<_Tp>::value || is_enum<_Tp>::value>
    struct __make_unsigned {};

    template <class _Tp>
    struct __make_unsigned<_Tp, true>
    {
        typedef typename __find_first<__unsigned_types, sizeof(_Tp)>::type type;
    };

    template <> struct __make_unsigned<bool,               true> {};
    template <> struct __make_unsigned<  signed short,     true> {typedef unsigned short     type;};
    template <> struct __make_unsigned<unsigned short,     true> {typedef unsigned short     type;};
    template <> struct __make_unsigned<  signed int,       true> {typedef unsigned int       type;};
    template <> struct __make_unsigned<unsigned int,       true> {typedef unsigned int       type;};
    template <> struct __make_unsigned<  signed long,      true> {typedef unsigned long      type;};
    template <> struct __make_unsigned<unsigned long,      true> {typedef unsigned long      type;};
    template <> struct __make_unsigned<  signed long long, true> {typedef unsigned long long type;};
    template <> struct __make_unsigned<unsigned long long, true> {typedef unsigned long long type;};
#ifndef __WI_LIBCPP_HAS_NO_INT128
    template <> struct __make_unsigned<__int128_t,         true> {typedef __uint128_t        type;};
    template <> struct __make_unsigned<__uint128_t,        true> {typedef __uint128_t        type;};
#endif

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS make_unsigned
    {
        typedef typename __apply_cv<_Tp, typename __make_unsigned<typename remove_cv<_Tp>::type>::type>::type type;
    };

#if __WI_LIBCPP_STD_VER > 11
    template <class _Tp> using make_unsigned_t = typename make_unsigned<_Tp>::type;
#endif

#ifdef __WI_LIBCPP_HAS_NO_VARIADICS

    template <class _Tp, class _Up = void, class _Vp = void>
    struct __WI_LIBCPP_TEMPLATE_VIS common_type
    {
    public:
        typedef typename common_type<typename common_type<_Tp, _Up>::type, _Vp>::type type;
    };

    template <>
    struct __WI_LIBCPP_TEMPLATE_VIS common_type<void, void, void>
    {
    public:
        typedef void type;
    };

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS common_type<_Tp, void, void>
    {
    public:
        typedef typename common_type<_Tp, _Tp>::type type;
    };

    template <class _Tp, class _Up>
    struct __WI_LIBCPP_TEMPLATE_VIS common_type<_Tp, _Up, void>
    {
        typedef typename decay<decltype(
            true ? declval<_Tp>() : declval<_Up>()
        )>::type type;
    };

#else  // __WI_LIBCPP_HAS_NO_VARIADICS

    // bullet 1 - sizeof...(Tp) == 0

    template <class ..._Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS common_type {};

    // bullet 2 - sizeof...(Tp) == 1

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS common_type<_Tp>
        : public common_type<_Tp, _Tp> {};

    // bullet 3 - sizeof...(Tp) == 2

    template <class _Tp, class _Up, class = void>
    struct __common_type2_imp {};

    template <class _Tp, class _Up>
    struct __common_type2_imp<_Tp, _Up,
        typename __void_t<decltype(
            true ? declval<_Tp>() : declval<_Up>()
        )>::type>
    {
        typedef typename decay<decltype(
            true ? declval<_Tp>() : declval<_Up>()
        )>::type type;
    };

    template <class _Tp, class _Up,
            class _DTp = typename decay<_Tp>::type,
            class _DUp = typename decay<_Up>::type>
    using __common_type2 =
    typename conditional<
        is_same<_Tp, _DTp>::value && is_same<_Up, _DUp>::value,
        __common_type2_imp<_Tp, _Up>,
        common_type<_DTp, _DUp>
    >::type;

    template <class _Tp, class _Up>
    struct __WI_LIBCPP_TEMPLATE_VIS common_type<_Tp, _Up>
        : __common_type2<_Tp, _Up> {};

    // bullet 4 - sizeof...(Tp) > 2

    template <class ...Tp> struct __common_types;

    template <class, class = void>
    struct __common_type_impl {};

    template <class _Tp, class _Up>
    struct __common_type_impl<
        __common_types<_Tp, _Up>,
        typename __void_t<typename common_type<_Tp, _Up>::type>::type>
    {
    typedef typename common_type<_Tp, _Up>::type type;
    };

    template <class _Tp, class _Up, class ..._Vp>
    struct __common_type_impl<__common_types<_Tp, _Up, _Vp...>,
        typename __void_t<typename common_type<_Tp, _Up>::type>::type>
    : __common_type_impl<
        __common_types<typename common_type<_Tp, _Up>::type, _Vp...> >
    {

    };

    template <class _Tp, class _Up, class ..._Vp>
    struct __WI_LIBCPP_TEMPLATE_VIS common_type<_Tp, _Up, _Vp...>
        : __common_type_impl<__common_types<_Tp, _Up, _Vp...> > {};

#if __WI_LIBCPP_STD_VER > 11
    template <class ..._Tp> using common_type_t = typename common_type<_Tp...>::type;
#endif

#endif  // __WI_LIBCPP_HAS_NO_VARIADICS

    // is_assignable

    template<typename, typename _Tp> struct __select_2nd { typedef _Tp type; };

    template <class _Tp, class _Arg>
    typename __select_2nd<decltype((declval<_Tp>() = declval<_Arg>())), true_type>::type
    __is_assignable_test(int);

    template <class, class>
    false_type __is_assignable_test(...);


    template <class _Tp, class _Arg, bool = is_void<_Tp>::value || is_void<_Arg>::value>
    struct __is_assignable_imp
        : public decltype((__is_assignable_test<_Tp, _Arg>(0))) {};

    template <class _Tp, class _Arg>
    struct __is_assignable_imp<_Tp, _Arg, true>
        : public false_type
    {
    };

    template <class _Tp, class _Arg>
    struct is_assignable
        : public __is_assignable_imp<_Tp, _Arg> {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp, class _Arg>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_assignable_v
        = is_assignable<_Tp, _Arg>::value;
#endif

    // is_copy_assignable

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_copy_assignable
        : public is_assignable<typename add_lvalue_reference<_Tp>::type,
                    typename add_lvalue_reference<typename add_const<_Tp>::type>::type> {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_copy_assignable_v
        = is_copy_assignable<_Tp>::value;
#endif

    // is_move_assignable

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_move_assignable
#ifndef __WI_LIBCPP_HAS_NO_RVALUE_REFERENCES
        : public is_assignable<typename add_lvalue_reference<_Tp>::type,
                            typename add_rvalue_reference<_Tp>::type> {};
#else
        : public is_copy_assignable<_Tp> {};
#endif

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_move_assignable_v
        = is_move_assignable<_Tp>::value;
#endif

    // is_destructible

#if __WI_HAS_FEATURE_IS_DESTRUCTIBLE

    template <class _Tp>
    struct is_destructible
        : public integral_constant<bool, __is_destructible(_Tp)> {};

#else

    //  if it's a reference, return true
    //  if it's a function, return false
    //  if it's   void,     return false
    //  if it's an array of unknown bound, return false
    //  Otherwise, return "std::declval<_Up&>().~_Up()" is well-formed
    //    where _Up is remove_all_extents<_Tp>::type

    template <class>
    struct __is_destructible_apply { typedef int type; };

    template <typename _Tp>
    struct __is_destructor_wellformed {
        template <typename _Tp1>
        static char  __test (
            typename __is_destructible_apply<decltype(declval<_Tp1&>().~_Tp1())>::type
        );

        template <typename _Tp1>
        static __two __test (...);

        static const bool value = sizeof(__test<_Tp>(12)) == sizeof(char);
    };

    template <class _Tp, bool>
    struct __destructible_imp;

    template <class _Tp>
    struct __destructible_imp<_Tp, false>
    : public integral_constant<bool,
            __is_destructor_wellformed<typename remove_all_extents<_Tp>::type>::value> {};

    template <class _Tp>
    struct __destructible_imp<_Tp, true>
        : public true_type {};

    template <class _Tp, bool>
    struct __destructible_false;

    template <class _Tp>
    struct __destructible_false<_Tp, false> : public __destructible_imp<_Tp, is_reference<_Tp>::value> {};

    template <class _Tp>
    struct __destructible_false<_Tp, true> : public false_type {};

    template <class _Tp>
    struct is_destructible
        : public __destructible_false<_Tp, is_function<_Tp>::value> {};

    template <class _Tp>
    struct is_destructible<_Tp[]>
        : public false_type {};

    template <>
    struct is_destructible<void>
        : public false_type {};

#endif // __WI_HAS_FEATURE_IS_DESTRUCTIBLE

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_destructible_v
        = is_destructible<_Tp>::value;
#endif

    // move

#ifndef __WI_LIBCPP_HAS_NO_RVALUE_REFERENCES

    template <class _Tp>
    inline __WI_LIBCPP_INLINE_VISIBILITY __WI_LIBCPP_CONSTEXPR
    typename remove_reference<_Tp>::type&&
    move(_Tp&& __t) WI_NOEXCEPT
    {
        typedef typename remove_reference<_Tp>::type _Up;
        return static_cast<_Up&&>(__t);
    }

    template <class _Tp>
    inline __WI_LIBCPP_INLINE_VISIBILITY __WI_LIBCPP_CONSTEXPR
    _Tp&&
    forward(typename remove_reference<_Tp>::type& __t) WI_NOEXCEPT
    {
        return static_cast<_Tp&&>(__t);
    }

    template <class _Tp>
    inline __WI_LIBCPP_INLINE_VISIBILITY __WI_LIBCPP_CONSTEXPR
    _Tp&&
    forward(typename remove_reference<_Tp>::type&& __t) WI_NOEXCEPT
    {
        static_assert(!is_lvalue_reference<_Tp>::value,
                    "can not forward an rvalue as an lvalue");
        return static_cast<_Tp&&>(__t);
    }

    template <class _T1, class _T2 = _T1>
    inline __WI_LIBCPP_INLINE_VISIBILITY __WI_LIBCPP_CONSTEXPR_AFTER_CXX17
    _T1 exchange(_T1& __obj, _T2 && __new_value)
    {
        _T1 __old_value = wistd::move(__obj);
        __obj = wistd::forward<_T2>(__new_value);
        return __old_value;
    }

#else  // __WI_LIBCPP_HAS_NO_RVALUE_REFERENCES

    template <class _Tp>
    inline __WI_LIBCPP_INLINE_VISIBILITY
    _Tp&
    move(_Tp& __t)
    {
        return __t;
    }

    template <class _Tp>
    inline __WI_LIBCPP_INLINE_VISIBILITY
    const _Tp&
    move(const _Tp& __t)
    {
        return __t;
    }

    template <class _Tp>
    inline __WI_LIBCPP_INLINE_VISIBILITY
    _Tp&
    forward(typename remove_reference<_Tp>::type& __t) WI_NOEXCEPT
    {
        return __t;
    }

    template <class _T1, class _T2 = _T1>
    inline __WI_LIBCPP_INLINE_VISIBILITY
    _T1 exchange(_T1& __obj, const _T2& __new_value)
    {
        _T1 __old_value = __obj;
        __obj = __new_value;
        return __old_value;
    }

    template <class _Tp>
    class __rv
    {
        typedef typename remove_reference<_Tp>::type _Trr;
        _Trr& t_;
    public:
        __WI_LIBCPP_INLINE_VISIBILITY
        _Trr* operator->() {return &t_;}
        __WI_LIBCPP_INLINE_VISIBILITY
        explicit __rv(_Trr& __t) : t_(__t) {}
    };

#endif  // __WI_LIBCPP_HAS_NO_RVALUE_REFERENCES

#if __WI_LIBCPP_STD_VER > 11
     template <class _Tp = void>
#else
     template <class _Tp>
#endif
     struct __WI_LIBCPP_TEMPLATE_VIS less : binary_function<_Tp, _Tp, bool>
     {
     __WI_LIBCPP_CONSTEXPR_AFTER_CXX11 __WI_LIBCPP_INLINE_VISIBILITY
     bool operator()(const _Tp& __x, const _Tp& __y) const
          {return __x < __y;}
     };

#if __WI_LIBCPP_STD_VER > 11
    template <>
    struct __WI_LIBCPP_TEMPLATE_VIS less<void>
    {
        template <class _T1, class _T2>
        __WI_LIBCPP_CONSTEXPR_AFTER_CXX11 __WI_LIBCPP_INLINE_VISIBILITY
        auto operator()(_T1&& __t, _T2&& __u) const
        __WI_NOEXCEPT_(noexcept(wistd::forward<_T1>(__t) < wistd::forward<_T2>(__u)))
        -> decltype        (wistd::forward<_T1>(__t) < wistd::forward<_T2>(__u))
            { return        wistd::forward<_T1>(__t) < wistd::forward<_T2>(__u); }
        typedef void is_transparent;
    };
#endif

#ifndef __WI_LIBCPP_HAS_NO_RVALUE_REFERENCES

    template <class _Tp>
    inline __WI_LIBCPP_INLINE_VISIBILITY
    typename decay<_Tp>::type
    __decay_copy(_Tp&& __t)
    {
        return wistd::forward<_Tp>(__t);
    }

#else

    template <class _Tp>
    inline __WI_LIBCPP_INLINE_VISIBILITY
    typename decay<_Tp>::type
    __decay_copy(const _Tp& __t)
    {
        return wistd::forward<_Tp>(__t);
    }

#endif

#ifndef __WI_LIBCPP_HAS_NO_VARIADICS

    template <class _Rp, class _Class, class ..._Param>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param...), true, false>
    {
        typedef _Class _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_Param...);
    };

    template <class _Rp, class _Class, class ..._Param>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param..., ...), true, false>
    {
        typedef _Class _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_Param..., ...);
    };

    template <class _Rp, class _Class, class ..._Param>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param...) const, true, false>
    {
        typedef _Class const _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_Param...);
    };

    template <class _Rp, class _Class, class ..._Param>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param..., ...) const, true, false>
    {
        typedef _Class const _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_Param..., ...);
    };

    template <class _Rp, class _Class, class ..._Param>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param...) volatile, true, false>
    {
        typedef _Class volatile _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_Param...);
    };

    template <class _Rp, class _Class, class ..._Param>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param..., ...) volatile, true, false>
    {
        typedef _Class volatile _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_Param..., ...);
    };

    template <class _Rp, class _Class, class ..._Param>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param...) const volatile, true, false>
    {
        typedef _Class const volatile _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_Param...);
    };

    template <class _Rp, class _Class, class ..._Param>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param..., ...) const volatile, true, false>
    {
        typedef _Class const volatile _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_Param..., ...);
    };

#if __WI_HAS_FEATURE_REFERENCE_QUALIFIED_FUNCTIONS || \
        (defined(__WI_GNUC_VER) && __WI_GNUC_VER >= 409)

    template <class _Rp, class _Class, class ..._Param>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param...) &, true, false>
    {
        typedef _Class& _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_Param...);
    };

    template <class _Rp, class _Class, class ..._Param>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param..., ...) &, true, false>
    {
        typedef _Class& _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_Param..., ...);
    };

    template <class _Rp, class _Class, class ..._Param>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param...) const&, true, false>
    {
        typedef _Class const& _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_Param...);
    };

    template <class _Rp, class _Class, class ..._Param>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param..., ...) const&, true, false>
    {
        typedef _Class const& _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_Param..., ...);
    };

    template <class _Rp, class _Class, class ..._Param>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param...) volatile&, true, false>
    {
        typedef _Class volatile& _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_Param...);
    };

    template <class _Rp, class _Class, class ..._Param>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param..., ...) volatile&, true, false>
    {
        typedef _Class volatile& _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_Param..., ...);
    };

    template <class _Rp, class _Class, class ..._Param>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param...) const volatile&, true, false>
    {
        typedef _Class const volatile& _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_Param...);
    };

    template <class _Rp, class _Class, class ..._Param>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param..., ...) const volatile&, true, false>
    {
        typedef _Class const volatile& _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_Param..., ...);
    };

    template <class _Rp, class _Class, class ..._Param>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param...) &&, true, false>
    {
        typedef _Class&& _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_Param...);
    };

    template <class _Rp, class _Class, class ..._Param>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param..., ...) &&, true, false>
    {
        typedef _Class&& _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_Param..., ...);
    };

    template <class _Rp, class _Class, class ..._Param>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param...) const&&, true, false>
    {
        typedef _Class const&& _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_Param...);
    };

    template <class _Rp, class _Class, class ..._Param>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param..., ...) const&&, true, false>
    {
        typedef _Class const&& _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_Param..., ...);
    };

    template <class _Rp, class _Class, class ..._Param>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param...) volatile&&, true, false>
    {
        typedef _Class volatile&& _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_Param...);
    };

    template <class _Rp, class _Class, class ..._Param>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param..., ...) volatile&&, true, false>
    {
        typedef _Class volatile&& _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_Param..., ...);
    };

    template <class _Rp, class _Class, class ..._Param>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param...) const volatile&&, true, false>
    {
        typedef _Class const volatile&& _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_Param...);
    };

    template <class _Rp, class _Class, class ..._Param>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param..., ...) const volatile&&, true, false>
    {
        typedef _Class const volatile&& _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_Param..., ...);
    };

#endif  // __WI_HAS_FEATURE_REFERENCE_QUALIFIED_FUNCTIONS || __WI_GNUC_VER >= 409

#else  // __WI_LIBCPP_HAS_NO_VARIADICS

    template <class _Rp, class _Class>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(), true, false>
    {
        typedef _Class _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) ();
    };

    template <class _Rp, class _Class>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(...), true, false>
    {
        typedef _Class _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (...);
    };

    template <class _Rp, class _Class, class _P0>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0), true, false>
    {
        typedef _Class _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_P0);
    };

    template <class _Rp, class _Class, class _P0>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0, ...), true, false>
    {
        typedef _Class _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_P0, ...);
    };

    template <class _Rp, class _Class, class _P0, class _P1>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0, _P1), true, false>
    {
        typedef _Class _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_P0, _P1);
    };

    template <class _Rp, class _Class, class _P0, class _P1>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0, _P1, ...), true, false>
    {
        typedef _Class _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_P0, _P1, ...);
    };

    template <class _Rp, class _Class, class _P0, class _P1, class _P2>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0, _P1, _P2), true, false>
    {
        typedef _Class _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_P0, _P1, _P2);
    };

    template <class _Rp, class _Class, class _P0, class _P1, class _P2>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0, _P1, _P2, ...), true, false>
    {
        typedef _Class _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_P0, _P1, _P2, ...);
    };

    template <class _Rp, class _Class>
    struct __member_pointer_traits_imp<_Rp (_Class::*)() const, true, false>
    {
        typedef _Class const _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) ();
    };

    template <class _Rp, class _Class>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(...) const, true, false>
    {
        typedef _Class const _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (...);
    };

    template <class _Rp, class _Class, class _P0>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0) const, true, false>
    {
        typedef _Class const _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_P0);
    };

    template <class _Rp, class _Class, class _P0>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0, ...) const, true, false>
    {
        typedef _Class const _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_P0, ...);
    };

    template <class _Rp, class _Class, class _P0, class _P1>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0, _P1) const, true, false>
    {
        typedef _Class const _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_P0, _P1);
    };

    template <class _Rp, class _Class, class _P0, class _P1>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0, _P1, ...) const, true, false>
    {
        typedef _Class const _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_P0, _P1, ...);
    };

    template <class _Rp, class _Class, class _P0, class _P1, class _P2>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0, _P1, _P2) const, true, false>
    {
        typedef _Class const _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_P0, _P1, _P2);
    };

    template <class _Rp, class _Class, class _P0, class _P1, class _P2>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0, _P1, _P2, ...) const, true, false>
    {
        typedef _Class const _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_P0, _P1, _P2, ...);
    };

    template <class _Rp, class _Class>
    struct __member_pointer_traits_imp<_Rp (_Class::*)() volatile, true, false>
    {
        typedef _Class volatile _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) ();
    };

    template <class _Rp, class _Class>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(...) volatile, true, false>
    {
        typedef _Class volatile _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (...);
    };

    template <class _Rp, class _Class, class _P0>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0) volatile, true, false>
    {
        typedef _Class volatile _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_P0);
    };

    template <class _Rp, class _Class, class _P0>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0, ...) volatile, true, false>
    {
        typedef _Class volatile _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_P0, ...);
    };

    template <class _Rp, class _Class, class _P0, class _P1>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0, _P1) volatile, true, false>
    {
        typedef _Class volatile _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_P0, _P1);
    };

    template <class _Rp, class _Class, class _P0, class _P1>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0, _P1, ...) volatile, true, false>
    {
        typedef _Class volatile _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_P0, _P1, ...);
    };

    template <class _Rp, class _Class, class _P0, class _P1, class _P2>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0, _P1, _P2) volatile, true, false>
    {
        typedef _Class volatile _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_P0, _P1, _P2);
    };

    template <class _Rp, class _Class, class _P0, class _P1, class _P2>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0, _P1, _P2, ...) volatile, true, false>
    {
        typedef _Class volatile _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_P0, _P1, _P2, ...);
    };

    template <class _Rp, class _Class>
    struct __member_pointer_traits_imp<_Rp (_Class::*)() const volatile, true, false>
    {
        typedef _Class const volatile _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) ();
    };

    template <class _Rp, class _Class>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(...) const volatile, true, false>
    {
        typedef _Class const volatile _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (...);
    };

    template <class _Rp, class _Class, class _P0>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0) const volatile, true, false>
    {
        typedef _Class const volatile _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_P0);
    };

    template <class _Rp, class _Class, class _P0>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0, ...) const volatile, true, false>
    {
        typedef _Class const volatile _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_P0, ...);
    };

    template <class _Rp, class _Class, class _P0, class _P1>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0, _P1) const volatile, true, false>
    {
        typedef _Class const volatile _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_P0, _P1);
    };

    template <class _Rp, class _Class, class _P0, class _P1>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0, _P1, ...) const volatile, true, false>
    {
        typedef _Class const volatile _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_P0, _P1, ...);
    };

    template <class _Rp, class _Class, class _P0, class _P1, class _P2>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0, _P1, _P2) const volatile, true, false>
    {
        typedef _Class const volatile _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_P0, _P1, _P2);
    };

    template <class _Rp, class _Class, class _P0, class _P1, class _P2>
    struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0, _P1, _P2, ...) const volatile, true, false>
    {
        typedef _Class const volatile _ClassType;
        typedef _Rp _ReturnType;
        typedef _Rp (_FnType) (_P0, _P1, _P2, ...);
    };

#endif  // __WI_LIBCPP_HAS_NO_VARIADICS

    template <class _Rp, class _Class>
    struct __member_pointer_traits_imp<_Rp _Class::*, false, true>
    {
        typedef _Class _ClassType;
        typedef _Rp _ReturnType;
    };

    template <class _Mp>
    struct __member_pointer_traits
        : public __member_pointer_traits_imp<typename remove_cv<_Mp>::type,
                        is_member_function_pointer<_Mp>::value,
                        is_member_object_pointer<_Mp>::value>
    {
    //     typedef ... _ClassType;
    //     typedef ... _ReturnType;
    //     typedef ... _FnType;
    };


    template <class _DecayedFp>
    struct __member_pointer_class_type {};

    template <class _Ret, class _ClassType>
    struct __member_pointer_class_type<_Ret _ClassType::*> {
    typedef _ClassType type;
    };

    // result_of

    template <class _Callable> class result_of;

#ifdef __WI_LIBCPP_HAS_NO_VARIADICS

    template <class _Fn, bool, bool>
    class __result_of
    {
    };

    template <class _Fn>
    class __result_of<_Fn(), true, false>
    {
    public:
        typedef decltype(declval<_Fn>()()) type;
    };

    template <class _Fn, class _A0>
    class __result_of<_Fn(_A0), true, false>
    {
    public:
        typedef decltype(declval<_Fn>()(declval<_A0>())) type;
    };

    template <class _Fn, class _A0, class _A1>
    class __result_of<_Fn(_A0, _A1), true, false>
    {
    public:
        typedef decltype(declval<_Fn>()(declval<_A0>(), declval<_A1>())) type;
    };

    template <class _Fn, class _A0, class _A1, class _A2>
    class __result_of<_Fn(_A0, _A1, _A2), true, false>
    {
    public:
        typedef decltype(declval<_Fn>()(declval<_A0>(), declval<_A1>(), declval<_A2>())) type;
    };

    template <class _Mp, class _Tp, bool _IsMemberFunctionPtr>
    struct __result_of_mp;

    // member function pointer

    template <class _Mp, class _Tp>
    struct __result_of_mp<_Mp, _Tp, true>
        : public __identity<typename __member_pointer_traits<_Mp>::_ReturnType>
    {
    };

    // member data pointer

    template <class _Mp, class _Tp, bool>
    struct __result_of_mdp;

    template <class _Rp, class _Class, class _Tp>
    struct __result_of_mdp<_Rp _Class::*, _Tp, false>
    {
        typedef typename __apply_cv<decltype(*declval<_Tp>()), _Rp>::type& type;
    };

    template <class _Rp, class _Class, class _Tp>
    struct __result_of_mdp<_Rp _Class::*, _Tp, true>
    {
        typedef typename __apply_cv<_Tp, _Rp>::type& type;
    };

    template <class _Rp, class _Class, class _Tp>
    struct __result_of_mp<_Rp _Class::*, _Tp, false>
        : public __result_of_mdp<_Rp _Class::*, _Tp,
                is_base_of<_Class, typename remove_reference<_Tp>::type>::value>
    {
    };



    template <class _Fn, class _Tp>
    class __result_of<_Fn(_Tp), false, true>  // _Fn must be member pointer
        : public __result_of_mp<typename remove_reference<_Fn>::type,
                                _Tp,
                                is_member_function_pointer<typename remove_reference<_Fn>::type>::value>
    {
    };

    template <class _Fn, class _Tp, class _A0>
    class __result_of<_Fn(_Tp, _A0), false, true>  // _Fn must be member pointer
        : public __result_of_mp<typename remove_reference<_Fn>::type,
                                _Tp,
                                is_member_function_pointer<typename remove_reference<_Fn>::type>::value>
    {
    };

    template <class _Fn, class _Tp, class _A0, class _A1>
    class __result_of<_Fn(_Tp, _A0, _A1), false, true>  // _Fn must be member pointer
        : public __result_of_mp<typename remove_reference<_Fn>::type,
                                _Tp,
                                is_member_function_pointer<typename remove_reference<_Fn>::type>::value>
    {
    };

    template <class _Fn, class _Tp, class _A0, class _A1, class _A2>
    class __result_of<_Fn(_Tp, _A0, _A1, _A2), false, true>  // _Fn must be member pointer
        : public __result_of_mp<typename remove_reference<_Fn>::type,
                                _Tp,
                                is_member_function_pointer<typename remove_reference<_Fn>::type>::value>
    {
    };

    // result_of

    template <class _Fn>
    class __WI_LIBCPP_TEMPLATE_VIS result_of<_Fn()>
        : public __result_of<_Fn(),
                            is_class<typename remove_reference<_Fn>::type>::value ||
                            is_function<typename remove_pointer<typename remove_reference<_Fn>::type>::type>::value,
                            is_member_pointer<typename remove_reference<_Fn>::type>::value
                            >
    {
    };

    template <class _Fn, class _A0>
    class __WI_LIBCPP_TEMPLATE_VIS result_of<_Fn(_A0)>
        : public __result_of<_Fn(_A0),
                            is_class<typename remove_reference<_Fn>::type>::value ||
                            is_function<typename remove_pointer<typename remove_reference<_Fn>::type>::type>::value,
                            is_member_pointer<typename remove_reference<_Fn>::type>::value
                            >
    {
    };

    template <class _Fn, class _A0, class _A1>
    class __WI_LIBCPP_TEMPLATE_VIS result_of<_Fn(_A0, _A1)>
        : public __result_of<_Fn(_A0, _A1),
                            is_class<typename remove_reference<_Fn>::type>::value ||
                            is_function<typename remove_pointer<typename remove_reference<_Fn>::type>::type>::value,
                            is_member_pointer<typename remove_reference<_Fn>::type>::value
                            >
    {
    };

    template <class _Fn, class _A0, class _A1, class _A2>
    class __WI_LIBCPP_TEMPLATE_VIS result_of<_Fn(_A0, _A1, _A2)>
        : public __result_of<_Fn(_A0, _A1, _A2),
                            is_class<typename remove_reference<_Fn>::type>::value ||
                            is_function<typename remove_pointer<typename remove_reference<_Fn>::type>::type>::value,
                            is_member_pointer<typename remove_reference<_Fn>::type>::value
                            >
    {
    };

#endif  // __WI_LIBCPP_HAS_NO_VARIADICS

    // template <class T, class... Args> struct is_constructible;

    namespace __is_construct
    {
    struct __nat {};
    }

#if !defined(__WI_LIBCPP_CXX03_LANG) && (!__WI_HAS_FEATURE_IS_CONSTRUCTIBLE || \
        defined(__WI_LIBCPP_TESTING_FALLBACK_IS_CONSTRUCTIBLE))

    template <class _Tp, class... _Args>
    struct __libcpp_is_constructible;

    template <class _To, class _From>
    struct __is_invalid_base_to_derived_cast {
    static_assert(is_reference<_To>::value, "Wrong specialization");
    using _RawFrom = __uncvref_t<_From>;
    using _RawTo = __uncvref_t<_To>;
    static const bool value = __lazy_and<
            __lazy_not<is_same<_RawFrom, _RawTo>>,
            is_base_of<_RawFrom, _RawTo>,
            __lazy_not<__libcpp_is_constructible<_RawTo, _From>>
    >::value;
    };

    template <class _To, class _From>
    struct __is_invalid_lvalue_to_rvalue_cast : false_type {
    static_assert(is_reference<_To>::value, "Wrong specialization");
    };

    template <class _ToRef, class _FromRef>
    struct __is_invalid_lvalue_to_rvalue_cast<_ToRef&&, _FromRef&> {
    using _RawFrom = __uncvref_t<_FromRef>;
    using _RawTo = __uncvref_t<_ToRef>;
    static const bool value = __lazy_and<
        __lazy_not<is_function<_RawTo>>,
        __lazy_or<
            is_same<_RawFrom, _RawTo>,
            is_base_of<_RawTo, _RawFrom>>
        >::value;
    };

    struct __is_constructible_helper
    {
        template <class _To>
        static void __eat(_To);

        // This overload is needed to work around a Clang bug that disallows
        // static_cast<T&&>(e) for non-reference-compatible types.
        // Example: static_cast<int&&>(declval<double>());
        // NOTE: The static_cast implementation below is required to support
        //  classes with explicit conversion operators.
        template <class _To, class _From,
                class = decltype(__eat<_To>(declval<_From>()))>
        static true_type __test_cast(int);

        template <class _To, class _From,
                class = decltype(static_cast<_To>(declval<_From>()))>
        static integral_constant<bool,
            !__is_invalid_base_to_derived_cast<_To, _From>::value &&
            !__is_invalid_lvalue_to_rvalue_cast<_To, _From>::value
        > __test_cast(long);

        template <class, class>
        static false_type __test_cast(...);

        template <class _Tp, class ..._Args,
            class = decltype(_Tp(declval<_Args>()...))>
        static true_type __test_nary(int);
        template <class _Tp, class...>
        static false_type __test_nary(...);

        template <class _Tp, class _A0, class = decltype(::new _Tp(declval<_A0>()))>
        static is_destructible<_Tp> __test_unary(int);
        template <class, class>
        static false_type __test_unary(...);
    };

    template <class _Tp, bool = is_void<_Tp>::value>
    struct __is_default_constructible
        : decltype(__is_constructible_helper::__test_nary<_Tp>(0))
    {};

    template <class _Tp>
    struct __is_default_constructible<_Tp, true> : false_type {};

    template <class _Tp>
    struct __is_default_constructible<_Tp[], false> : false_type {};

    template <class _Tp, size_t _Nx>
    struct __is_default_constructible<_Tp[_Nx], false>
        : __is_default_constructible<typename remove_all_extents<_Tp>::type>  {};

    template <class _Tp, class... _Args>
    struct __libcpp_is_constructible
    {
    static_assert(sizeof...(_Args) > 1, "Wrong specialization");
    typedef decltype(__is_constructible_helper::__test_nary<_Tp, _Args...>(0))
        type;
    };

    template <class _Tp>
    struct __libcpp_is_constructible<_Tp> : __is_default_constructible<_Tp> {};

    template <class _Tp, class _A0>
    struct __libcpp_is_constructible<_Tp, _A0>
        : public decltype(__is_constructible_helper::__test_unary<_Tp, _A0>(0))
    {};

    template <class _Tp, class _A0>
    struct __libcpp_is_constructible<_Tp&, _A0>
        : public decltype(__is_constructible_helper::
        __test_cast<_Tp&, _A0>(0))
    {};

    template <class _Tp, class _A0>
    struct __libcpp_is_constructible<_Tp&&, _A0>
        : public decltype(__is_constructible_helper::
        __test_cast<_Tp&&, _A0>(0))
    {};

#endif

#if __WI_HAS_FEATURE_IS_CONSTRUCTIBLE
    template <class _Tp, class ..._Args>
    struct __WI_LIBCPP_TEMPLATE_VIS is_constructible
        : public integral_constant<bool, __is_constructible(_Tp, _Args...)>
        {};
#elif !defined(__WI_LIBCPP_CXX03_LANG)
    template <class _Tp, class... _Args>
    struct __WI_LIBCPP_TEMPLATE_VIS is_constructible
        : public __libcpp_is_constructible<_Tp, _Args...>::type {};
#else
    // template <class T> struct is_constructible0;

    //      main is_constructible0 test

    template <class _Tp>
    decltype((_Tp(), true_type()))
    __is_constructible0_test(_Tp&);

    false_type
    __is_constructible0_test(__any);

    template <class _Tp, class _A0>
    decltype((_Tp(declval<_A0>()), true_type()))
    __is_constructible1_test(_Tp&, _A0&);

    template <class _A0>
    false_type
    __is_constructible1_test(__any, _A0&);

    template <class _Tp, class _A0, class _A1>
    decltype((_Tp(declval<_A0>(), declval<_A1>()), true_type()))
    __is_constructible2_test(_Tp&, _A0&, _A1&);

    template <class _A0, class _A1>
    false_type
    __is_constructible2_test(__any, _A0&, _A1&);

    template <class _Tp, class _A0, class _A1, class _A2>
    decltype((_Tp(declval<_A0>(), declval<_A1>(), declval<_A2>()), true_type()))
    __is_constructible3_test(_Tp&, _A0&, _A1&, _A2&);

    template <class _A0, class _A1, class _A2>
    false_type
    __is_constructible3_test(__any, _A0&, _A1&, _A2&);

    template <bool, class _Tp>
    struct __is_constructible0_imp // false, _Tp is not a scalar
        : public common_type
                <
                    decltype(__is_constructible0_test(declval<_Tp&>()))
                >::type
        {};

    template <bool, class _Tp, class _A0>
    struct __is_constructible1_imp // false, _Tp is not a scalar
        : public common_type
                <
                    decltype(__is_constructible1_test(declval<_Tp&>(), declval<_A0&>()))
                >::type
        {};

    template <bool, class _Tp, class _A0, class _A1>
    struct __is_constructible2_imp // false, _Tp is not a scalar
        : public common_type
                <
                    decltype(__is_constructible2_test(declval<_Tp&>(), declval<_A0>(), declval<_A1>()))
                >::type
        {};

    template <bool, class _Tp, class _A0, class _A1, class _A2>
    struct __is_constructible3_imp // false, _Tp is not a scalar
        : public common_type
                <
                    decltype(__is_constructible3_test(declval<_Tp&>(), declval<_A0>(), declval<_A1>(), declval<_A2>()))
                >::type
        {};

    //      handle scalars and reference types

    //      Scalars are default constructible, references are not

    template <class _Tp>
    struct __is_constructible0_imp<true, _Tp>
        : public is_scalar<_Tp>
        {};

    template <class _Tp, class _A0>
    struct __is_constructible1_imp<true, _Tp, _A0>
        : public is_convertible<_A0, _Tp>
        {};

    template <class _Tp, class _A0, class _A1>
    struct __is_constructible2_imp<true, _Tp, _A0, _A1>
        : public false_type
        {};

    template <class _Tp, class _A0, class _A1, class _A2>
    struct __is_constructible3_imp<true, _Tp, _A0, _A1, _A2>
        : public false_type
        {};

    //      Treat scalars and reference types separately

    template <bool, class _Tp>
    struct __is_constructible0_void_check
        : public __is_constructible0_imp<is_scalar<_Tp>::value || is_reference<_Tp>::value,
                                    _Tp>
        {};

    template <bool, class _Tp, class _A0>
    struct __is_constructible1_void_check
        : public __is_constructible1_imp<is_scalar<_Tp>::value || is_reference<_Tp>::value,
                                    _Tp, _A0>
        {};

    template <bool, class _Tp, class _A0, class _A1>
    struct __is_constructible2_void_check
        : public __is_constructible2_imp<is_scalar<_Tp>::value || is_reference<_Tp>::value,
                                    _Tp, _A0, _A1>
        {};

    template <bool, class _Tp, class _A0, class _A1, class _A2>
    struct __is_constructible3_void_check
        : public __is_constructible3_imp<is_scalar<_Tp>::value || is_reference<_Tp>::value,
                                    _Tp, _A0, _A1, _A2>
        {};

    //      If any of T or Args is void, is_constructible should be false

    template <class _Tp>
    struct __is_constructible0_void_check<true, _Tp>
        : public false_type
        {};

    template <class _Tp, class _A0>
    struct __is_constructible1_void_check<true, _Tp, _A0>
        : public false_type
        {};

    template <class _Tp, class _A0, class _A1>
    struct __is_constructible2_void_check<true, _Tp, _A0, _A1>
        : public false_type
        {};

    template <class _Tp, class _A0, class _A1, class _A2>
    struct __is_constructible3_void_check<true, _Tp, _A0, _A1, _A2>
        : public false_type
        {};

    //      is_constructible entry point

    template <class _Tp, class _A0 = __is_construct::__nat,
                        class _A1 = __is_construct::__nat,
                        class _A2 = __is_construct::__nat>
    struct __WI_LIBCPP_TEMPLATE_VIS is_constructible
        : public __is_constructible3_void_check<is_void<_Tp>::value
                                            || is_abstract<_Tp>::value
                                            || is_function<_Tp>::value
                                            || is_void<_A0>::value
                                            || is_void<_A1>::value
                                            || is_void<_A2>::value,
                                            _Tp, _A0, _A1, _A2>
        {};

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_constructible<_Tp, __is_construct::__nat, __is_construct::__nat>
        : public __is_constructible0_void_check<is_void<_Tp>::value
                                            || is_abstract<_Tp>::value
                                            || is_function<_Tp>::value,
                                            _Tp>
        {};

    template <class _Tp, class _A0>
    struct __WI_LIBCPP_TEMPLATE_VIS is_constructible<_Tp, _A0, __is_construct::__nat>
        : public __is_constructible1_void_check<is_void<_Tp>::value
                                            || is_abstract<_Tp>::value
                                            || is_function<_Tp>::value
                                            || is_void<_A0>::value,
                                            _Tp, _A0>
        {};

    template <class _Tp, class _A0, class _A1>
    struct __WI_LIBCPP_TEMPLATE_VIS is_constructible<_Tp, _A0, _A1, __is_construct::__nat>
        : public __is_constructible2_void_check<is_void<_Tp>::value
                                            || is_abstract<_Tp>::value
                                            || is_function<_Tp>::value
                                            || is_void<_A0>::value
                                            || is_void<_A1>::value,
                                            _Tp, _A0, _A1>
        {};

    //      Array types are default constructible if their element type
    //      is default constructible

    template <class _Ap, size_t _Np>
    struct __is_constructible0_imp<false, _Ap[_Np]>
        : public is_constructible<typename remove_all_extents<_Ap>::type>
        {};

    template <class _Ap, size_t _Np, class _A0>
    struct __is_constructible1_imp<false, _Ap[_Np], _A0>
        : public false_type
        {};

    template <class _Ap, size_t _Np, class _A0, class _A1>
    struct __is_constructible2_imp<false, _Ap[_Np], _A0, _A1>
        : public false_type
        {};

    template <class _Ap, size_t _Np, class _A0, class _A1, class _A2>
    struct __is_constructible3_imp<false, _Ap[_Np], _A0, _A1, _A2>
        : public false_type
        {};

    //      Incomplete array types are not constructible

    template <class _Ap>
    struct __is_constructible0_imp<false, _Ap[]>
        : public false_type
        {};

    template <class _Ap, class _A0>
    struct __is_constructible1_imp<false, _Ap[], _A0>
        : public false_type
        {};

    template <class _Ap, class _A0, class _A1>
    struct __is_constructible2_imp<false, _Ap[], _A0, _A1>
        : public false_type
        {};

    template <class _Ap, class _A0, class _A1, class _A2>
    struct __is_constructible3_imp<false, _Ap[], _A0, _A1, _A2>
        : public false_type
        {};

#endif // __WI_HAS_FEATURE_IS_CONSTRUCTIBLE


#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES) && !defined(__WI_LIBCPP_HAS_NO_VARIADICS)
    template <class _Tp, class ..._Args>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_constructible_v
        = is_constructible<_Tp, _Args...>::value;
#endif

    // is_default_constructible

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_default_constructible
        : public is_constructible<_Tp>
        {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_default_constructible_v
        = is_default_constructible<_Tp>::value;
#endif

    // is_copy_constructible

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_copy_constructible
        : public is_constructible<_Tp,
                    typename add_lvalue_reference<typename add_const<_Tp>::type>::type> {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_copy_constructible_v
        = is_copy_constructible<_Tp>::value;
#endif

    // is_move_constructible

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_move_constructible
#ifndef __WI_LIBCPP_HAS_NO_RVALUE_REFERENCES
        : public is_constructible<_Tp, typename add_rvalue_reference<_Tp>::type>
#else
        : public is_copy_constructible<_Tp>
#endif
        {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_move_constructible_v
        = is_move_constructible<_Tp>::value;
#endif

    // is_trivially_constructible

#ifndef __WI_LIBCPP_HAS_NO_VARIADICS

#if __WI_HAS_FEATURE_IS_TRIVIALLY_CONSTRUCTIBLE || __WI_GNUC_VER >= 501

    template <class _Tp, class... _Args>
    struct __WI_LIBCPP_TEMPLATE_VIS is_trivially_constructible
        : integral_constant<bool, __is_trivially_constructible(_Tp, _Args...)>
    {
    };

#else  // !__WI_HAS_FEATURE_IS_TRIVIALLY_CONSTRUCTIBLE

    template <class _Tp, class... _Args>
    struct __WI_LIBCPP_TEMPLATE_VIS is_trivially_constructible
        : false_type
    {
    };

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_trivially_constructible<_Tp>
#if __WI_HAS_FEATURE_HAS_TRIVIAL_CONSTRUCTOR
        : integral_constant<bool, __has_trivial_constructor(_Tp)>
#else
        : integral_constant<bool, is_scalar<_Tp>::value>
#endif
    {
    };

    template <class _Tp>
#ifndef __WI_LIBCPP_HAS_NO_RVALUE_REFERENCES
    struct __WI_LIBCPP_TEMPLATE_VIS is_trivially_constructible<_Tp, _Tp&&>
#else
    struct __WI_LIBCPP_TEMPLATE_VIS is_trivially_constructible<_Tp, _Tp>
#endif
        : integral_constant<bool, is_scalar<_Tp>::value>
    {
    };

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_trivially_constructible<_Tp, const _Tp&>
        : integral_constant<bool, is_scalar<_Tp>::value>
    {
    };

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_trivially_constructible<_Tp, _Tp&>
        : integral_constant<bool, is_scalar<_Tp>::value>
    {
    };

#endif  // !__WI_HAS_FEATURE_IS_TRIVIALLY_CONSTRUCTIBLE

#else  // __WI_LIBCPP_HAS_NO_VARIADICS

    template <class _Tp, class _A0 = __is_construct::__nat,
                        class _A1 = __is_construct::__nat>
    struct __WI_LIBCPP_TEMPLATE_VIS is_trivially_constructible
        : false_type
    {
    };

#if __WI_HAS_FEATURE_IS_TRIVIALLY_CONSTRUCTIBLE || __WI_GNUC_VER >= 501

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_trivially_constructible<_Tp, __is_construct::__nat,
                                                        __is_construct::__nat>
        : integral_constant<bool, __is_trivially_constructible(_Tp)>
    {
    };

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_trivially_constructible<_Tp, _Tp,
                                                        __is_construct::__nat>
        : integral_constant<bool, __is_trivially_constructible(_Tp, _Tp)>
    {
    };

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_trivially_constructible<_Tp, const _Tp&,
                                                        __is_construct::__nat>
        : integral_constant<bool, __is_trivially_constructible(_Tp, const _Tp&)>
    {
    };

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_trivially_constructible<_Tp, _Tp&,
                                                        __is_construct::__nat>
        : integral_constant<bool, __is_trivially_constructible(_Tp, _Tp&)>
    {
    };

#else  // !__WI_HAS_FEATURE_IS_TRIVIALLY_CONSTRUCTIBLE

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_trivially_constructible<_Tp, __is_construct::__nat,
                                                        __is_construct::__nat>
        : integral_constant<bool, is_scalar<_Tp>::value>
    {
    };

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_trivially_constructible<_Tp, _Tp,
                                                        __is_construct::__nat>
        : integral_constant<bool, is_scalar<_Tp>::value>
    {
    };

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_trivially_constructible<_Tp, const _Tp&,
                                                        __is_construct::__nat>
        : integral_constant<bool, is_scalar<_Tp>::value>
    {
    };

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_trivially_constructible<_Tp, _Tp&,
                                                        __is_construct::__nat>
        : integral_constant<bool, is_scalar<_Tp>::value>
    {
    };

#endif  // !__WI_HAS_FEATURE_IS_TRIVIALLY_CONSTRUCTIBLE

#endif  // __WI_LIBCPP_HAS_NO_VARIADICS

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES) && !defined(__WI_LIBCPP_HAS_NO_VARIADICS)
    template <class _Tp, class... _Args>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_trivially_constructible_v
        = is_trivially_constructible<_Tp, _Args...>::value;
#endif

    // is_trivially_default_constructible

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_trivially_default_constructible
        : public is_trivially_constructible<_Tp>
        {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_trivially_default_constructible_v
        = is_trivially_default_constructible<_Tp>::value;
#endif

    // is_trivially_copy_constructible

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_trivially_copy_constructible
        : public is_trivially_constructible<_Tp, typename add_lvalue_reference<const _Tp>::type>
        {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_trivially_copy_constructible_v
        = is_trivially_copy_constructible<_Tp>::value;
#endif

    // is_trivially_move_constructible

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_trivially_move_constructible
#ifndef __WI_LIBCPP_HAS_NO_RVALUE_REFERENCES
        : public is_trivially_constructible<_Tp, typename add_rvalue_reference<_Tp>::type>
#else
        : public is_trivially_copy_constructible<_Tp>
#endif
        {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_trivially_move_constructible_v
        = is_trivially_move_constructible<_Tp>::value;
#endif

    // is_trivially_assignable

#if __WI_HAS_FEATURE_IS_TRIVIALLY_ASSIGNABLE || __WI_GNUC_VER >= 501

    template <class _Tp, class _Arg>
    struct is_trivially_assignable
        : integral_constant<bool, __is_trivially_assignable(_Tp, _Arg)>
    {
    };

#else  // !__WI_HAS_FEATURE_IS_TRIVIALLY_ASSIGNABLE

    template <class _Tp, class _Arg>
    struct is_trivially_assignable
        : public false_type {};

    template <class _Tp>
    struct is_trivially_assignable<_Tp&, _Tp>
        : integral_constant<bool, is_scalar<_Tp>::value> {};

    template <class _Tp>
    struct is_trivially_assignable<_Tp&, _Tp&>
        : integral_constant<bool, is_scalar<_Tp>::value> {};

    template <class _Tp>
    struct is_trivially_assignable<_Tp&, const _Tp&>
        : integral_constant<bool, is_scalar<_Tp>::value> {};

#ifndef __WI_LIBCPP_HAS_NO_RVALUE_REFERENCES

    template <class _Tp>
    struct is_trivially_assignable<_Tp&, _Tp&&>
        : integral_constant<bool, is_scalar<_Tp>::value> {};

#endif  // __WI_LIBCPP_HAS_NO_RVALUE_REFERENCES

#endif  // !__WI_HAS_FEATURE_IS_TRIVIALLY_ASSIGNABLE

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp, class _Arg>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_trivially_assignable_v
        = is_trivially_assignable<_Tp, _Arg>::value;
#endif

    // is_trivially_copy_assignable

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_trivially_copy_assignable
        : public is_trivially_assignable<typename add_lvalue_reference<_Tp>::type,
                    typename add_lvalue_reference<typename add_const<_Tp>::type>::type> {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_trivially_copy_assignable_v
        = is_trivially_copy_assignable<_Tp>::value;
#endif

    // is_trivially_move_assignable

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_trivially_move_assignable
        : public is_trivially_assignable<typename add_lvalue_reference<_Tp>::type,
#ifndef __WI_LIBCPP_HAS_NO_RVALUE_REFERENCES
                                        typename add_rvalue_reference<_Tp>::type>
#else
                                        typename add_lvalue_reference<_Tp>::type>
#endif
        {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_trivially_move_assignable_v
        = is_trivially_move_assignable<_Tp>::value;
#endif

    // is_trivially_destructible

#if __WI_HAS_FEATURE_HAS_TRIVIAL_DESTRUCTOR || (__WI_GNUC_VER >= 403)

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_trivially_destructible
        : public integral_constant<bool, is_destructible<_Tp>::value && __has_trivial_destructor(_Tp)> {};

#else

    template <class _Tp> struct __libcpp_trivial_destructor
        : public integral_constant<bool, is_scalar<_Tp>::value ||
                                        is_reference<_Tp>::value> {};

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_trivially_destructible
        : public __libcpp_trivial_destructor<typename remove_all_extents<_Tp>::type> {};

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_trivially_destructible<_Tp[]>
        : public false_type {};

#endif

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_trivially_destructible_v
        = is_trivially_destructible<_Tp>::value;
#endif

    // is_nothrow_constructible

#if 0
    template <class _Tp, class... _Args>
    struct __WI_LIBCPP_TEMPLATE_VIS is_nothrow_constructible
        : public integral_constant<bool, __is_nothrow_constructible(_Tp(_Args...))>
    {
    };

#else

#ifndef __WI_LIBCPP_HAS_NO_VARIADICS

#if !defined(__WI_LIBCPP_HAS_NO_NOEXCEPT) || (__WI_GNUC_VER >= 407 && __cplusplus >= 201103L)

    template <bool, bool, class _Tp, class... _Args> struct __libcpp_is_nothrow_constructible;

    template <class _Tp, class... _Args>
    struct __libcpp_is_nothrow_constructible</*is constructible*/true, /*is reference*/false, _Tp, _Args...>
        : public integral_constant<bool, noexcept(_Tp(declval<_Args>()...))>
    {
    };

    template <class _Tp>
    void __implicit_conversion_to(_Tp) noexcept { }

    template <class _Tp, class _Arg>
    struct __libcpp_is_nothrow_constructible</*is constructible*/true, /*is reference*/true, _Tp, _Arg>
        : public integral_constant<bool, noexcept(__implicit_conversion_to<_Tp>(declval<_Arg>()))>
    {
    };

    template <class _Tp, bool _IsReference, class... _Args>
    struct __libcpp_is_nothrow_constructible</*is constructible*/false, _IsReference, _Tp, _Args...>
        : public false_type
    {
    };

    template <class _Tp, class... _Args>
    struct __WI_LIBCPP_TEMPLATE_VIS is_nothrow_constructible
        : __libcpp_is_nothrow_constructible<is_constructible<_Tp, _Args...>::value, is_reference<_Tp>::value, _Tp, _Args...>
    {
    };

    template <class _Tp, size_t _Ns>
    struct __WI_LIBCPP_TEMPLATE_VIS is_nothrow_constructible<_Tp[_Ns]>
        : __libcpp_is_nothrow_constructible<is_constructible<_Tp>::value, is_reference<_Tp>::value, _Tp>
    {
    };

#else  // !defined(__WI_LIBCPP_HAS_NO_NOEXCEPT)

    template <class _Tp, class... _Args>
    struct __WI_LIBCPP_TEMPLATE_VIS is_nothrow_constructible
        : false_type
    {
    };

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_nothrow_constructible<_Tp>
#if __WI_HAS_FEATURE_HAS_NOTHROW_CONSTRUCTOR
        : integral_constant<bool, __has_nothrow_constructor(_Tp)>
#else
        : integral_constant<bool, is_scalar<_Tp>::value>
#endif
    {
    };

    template <class _Tp>
#ifndef __WI_LIBCPP_HAS_NO_RVALUE_REFERENCES
    struct __WI_LIBCPP_TEMPLATE_VIS is_nothrow_constructible<_Tp, _Tp&&>
#else
    struct __WI_LIBCPP_TEMPLATE_VIS is_nothrow_constructible<_Tp, _Tp>
#endif
#if __WI_HAS_FEATURE_HAS_NOTHROW_COPY
        : integral_constant<bool, __has_nothrow_copy(_Tp)>
#else
        : integral_constant<bool, is_scalar<_Tp>::value>
#endif
    {
    };

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_nothrow_constructible<_Tp, const _Tp&>
#if __WI_HAS_FEATURE_HAS_NOTHROW_COPY
        : integral_constant<bool, __has_nothrow_copy(_Tp)>
#else
        : integral_constant<bool, is_scalar<_Tp>::value>
#endif
    {
    };

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_nothrow_constructible<_Tp, _Tp&>
#if __WI_HAS_FEATURE_HAS_NOTHROW_COPY
        : integral_constant<bool, __has_nothrow_copy(_Tp)>
#else
        : integral_constant<bool, is_scalar<_Tp>::value>
#endif
    {
    };

#endif  // !defined(__WI_LIBCPP_HAS_NO_NOEXCEPT)

#else  // __WI_LIBCPP_HAS_NO_VARIADICS

    template <class _Tp, class _A0 = __is_construct::__nat,
                        class _A1 = __is_construct::__nat>
    struct __WI_LIBCPP_TEMPLATE_VIS is_nothrow_constructible
        : false_type
    {
    };

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_nothrow_constructible<_Tp, __is_construct::__nat,
                                                        __is_construct::__nat>
#if __WI_HAS_FEATURE_HAS_NOTHROW_CONSTRUCTOR
        : integral_constant<bool, __has_nothrow_constructor(_Tp)>
#else
        : integral_constant<bool, is_scalar<_Tp>::value>
#endif
    {
    };

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_nothrow_constructible<_Tp, _Tp,
                                                        __is_construct::__nat>
#if __WI_HAS_FEATURE_HAS_NOTHROW_COPY
        : integral_constant<bool, __has_nothrow_copy(_Tp)>
#else
        : integral_constant<bool, is_scalar<_Tp>::value>
#endif
    {
    };

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_nothrow_constructible<_Tp, const _Tp&,
                                                        __is_construct::__nat>
#if __WI_HAS_FEATURE_HAS_NOTHROW_COPY
        : integral_constant<bool, __has_nothrow_copy(_Tp)>
#else
        : integral_constant<bool, is_scalar<_Tp>::value>
#endif
    {
    };

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_nothrow_constructible<_Tp, _Tp&,
                                                        __is_construct::__nat>
#if __WI_HAS_FEATURE_HAS_NOTHROW_COPY
        : integral_constant<bool, __has_nothrow_copy(_Tp)>
#else
        : integral_constant<bool, is_scalar<_Tp>::value>
#endif
    {
    };

#endif  // __WI_LIBCPP_HAS_NO_VARIADICS
#endif  // __has_feature(is_nothrow_constructible)

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES) && !defined(__WI_LIBCPP_HAS_NO_VARIADICS)
    template <class _Tp, class ..._Args>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_nothrow_constructible_v
        = is_nothrow_constructible<_Tp, _Args...>::value;
#endif

    // is_nothrow_default_constructible

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_nothrow_default_constructible
        : public is_nothrow_constructible<_Tp>
        {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_nothrow_default_constructible_v
        = is_nothrow_default_constructible<_Tp>::value;
#endif

    // is_nothrow_copy_constructible

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_nothrow_copy_constructible
        : public is_nothrow_constructible<_Tp,
                    typename add_lvalue_reference<typename add_const<_Tp>::type>::type> {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_nothrow_copy_constructible_v
        = is_nothrow_copy_constructible<_Tp>::value;
#endif

    // is_nothrow_move_constructible

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_nothrow_move_constructible
#ifndef __WI_LIBCPP_HAS_NO_RVALUE_REFERENCES
        : public is_nothrow_constructible<_Tp, typename add_rvalue_reference<_Tp>::type>
#else
        : public is_nothrow_copy_constructible<_Tp>
#endif
        {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_nothrow_move_constructible_v
        = is_nothrow_move_constructible<_Tp>::value;
#endif

    // is_nothrow_assignable

#if !defined(__WI_LIBCPP_HAS_NO_NOEXCEPT) || (__WI_GNUC_VER >= 407 && __cplusplus >= 201103L)

    template <bool, class _Tp, class _Arg> struct __libcpp_is_nothrow_assignable;

    template <class _Tp, class _Arg>
    struct __libcpp_is_nothrow_assignable<false, _Tp, _Arg>
        : public false_type
    {
    };

    template <class _Tp, class _Arg>
    struct __libcpp_is_nothrow_assignable<true, _Tp, _Arg>
        : public integral_constant<bool, noexcept(declval<_Tp>() = declval<_Arg>()) >
    {
    };

    template <class _Tp, class _Arg>
    struct __WI_LIBCPP_TEMPLATE_VIS is_nothrow_assignable
        : public __libcpp_is_nothrow_assignable<is_assignable<_Tp, _Arg>::value, _Tp, _Arg>
    {
    };

#else  // !defined(__WI_LIBCPP_HAS_NO_NOEXCEPT)

    template <class _Tp, class _Arg>
    struct __WI_LIBCPP_TEMPLATE_VIS is_nothrow_assignable
        : public false_type {};

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_nothrow_assignable<_Tp&, _Tp>
#if __WI_HAS_FEATURE_HAS_NOTHROW_ASSIGN
        : integral_constant<bool, __has_nothrow_assign(_Tp)> {};
#else
        : integral_constant<bool, is_scalar<_Tp>::value> {};
#endif

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_nothrow_assignable<_Tp&, _Tp&>
#if __WI_HAS_FEATURE_HAS_NOTHROW_ASSIGN
        : integral_constant<bool, __has_nothrow_assign(_Tp)> {};
#else
        : integral_constant<bool, is_scalar<_Tp>::value> {};
#endif

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_nothrow_assignable<_Tp&, const _Tp&>
#if __WI_HAS_FEATURE_HAS_NOTHROW_ASSIGN
        : integral_constant<bool, __has_nothrow_assign(_Tp)> {};
#else
        : integral_constant<bool, is_scalar<_Tp>::value> {};
#endif

#ifndef __WI_LIBCPP_HAS_NO_RVALUE_REFERENCES

    template <class _Tp>
    struct is_nothrow_assignable<_Tp&, _Tp&&>
#if __WI_HAS_FEATURE_HAS_NOTHROW_ASSIGN
        : integral_constant<bool, __has_nothrow_assign(_Tp)> {};
#else
        : integral_constant<bool, is_scalar<_Tp>::value> {};
#endif

#endif  // __WI_LIBCPP_HAS_NO_RVALUE_REFERENCES

#endif  // !defined(__WI_LIBCPP_HAS_NO_NOEXCEPT)

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp, class _Arg>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_nothrow_assignable_v
        = is_nothrow_assignable<_Tp, _Arg>::value;
#endif

    // is_nothrow_copy_assignable

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_nothrow_copy_assignable
        : public is_nothrow_assignable<typename add_lvalue_reference<_Tp>::type,
                    typename add_lvalue_reference<typename add_const<_Tp>::type>::type> {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_nothrow_copy_assignable_v
        = is_nothrow_copy_assignable<_Tp>::value;
#endif

    // is_nothrow_move_assignable

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_nothrow_move_assignable
        : public is_nothrow_assignable<typename add_lvalue_reference<_Tp>::type,
#ifndef __WI_LIBCPP_HAS_NO_RVALUE_REFERENCES
                                        typename add_rvalue_reference<_Tp>::type>
#else
                                        typename add_lvalue_reference<_Tp>::type>
#endif
        {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_nothrow_move_assignable_v
        = is_nothrow_move_assignable<_Tp>::value;
#endif

    // is_nothrow_destructible

#if !defined(__WI_LIBCPP_HAS_NO_NOEXCEPT) || (__WI_GNUC_VER >= 407 && __cplusplus >= 201103L)

    template <bool, class _Tp> struct __libcpp_is_nothrow_destructible;

    template <class _Tp>
    struct __libcpp_is_nothrow_destructible<false, _Tp>
        : public false_type
    {
    };

    template <class _Tp>
    struct __libcpp_is_nothrow_destructible<true, _Tp>
        : public integral_constant<bool, noexcept(declval<_Tp>().~_Tp()) >
    {
    };

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_nothrow_destructible
        : public __libcpp_is_nothrow_destructible<is_destructible<_Tp>::value, _Tp>
    {
    };

    template <class _Tp, size_t _Ns>
    struct __WI_LIBCPP_TEMPLATE_VIS is_nothrow_destructible<_Tp[_Ns]>
        : public is_nothrow_destructible<_Tp>
    {
    };

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_nothrow_destructible<_Tp&>
        : public true_type
    {
    };

#ifndef __WI_LIBCPP_HAS_NO_RVALUE_REFERENCES

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_nothrow_destructible<_Tp&&>
        : public true_type
    {
    };

#endif

#else

    template <class _Tp> struct __libcpp_nothrow_destructor
        : public integral_constant<bool, is_scalar<_Tp>::value ||
                                        is_reference<_Tp>::value> {};

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_nothrow_destructible
        : public __libcpp_nothrow_destructor<typename remove_all_extents<_Tp>::type> {};

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_nothrow_destructible<_Tp[]>
        : public false_type {};

#endif

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_nothrow_destructible_v
        = is_nothrow_destructible<_Tp>::value;
#endif

    // is_pod

#if __WI_HAS_FEATURE_IS_POD || (__WI_GNUC_VER >= 403)

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_pod
        : public integral_constant<bool, __is_pod(_Tp)> {};

#else

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_pod
        : public integral_constant<bool, is_trivially_default_constructible<_Tp>::value   &&
                                        is_trivially_copy_constructible<_Tp>::value      &&
                                        is_trivially_copy_assignable<_Tp>::value    &&
                                        is_trivially_destructible<_Tp>::value> {};

#endif

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_pod_v
        = is_pod<_Tp>::value;
#endif

    // is_literal_type;

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_literal_type
#ifdef __WI_LIBCPP_IS_LITERAL
        : public integral_constant<bool, __WI_LIBCPP_IS_LITERAL(_Tp)>
#else
        : integral_constant<bool, is_scalar<typename remove_all_extents<_Tp>::type>::value ||
                                is_reference<typename remove_all_extents<_Tp>::type>::value>
#endif
        {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_literal_type_v
        = is_literal_type<_Tp>::value;
#endif

    // is_standard_layout;

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_standard_layout
#if __WI_HAS_FEATURE_IS_STANDARD_LAYOUT || (__WI_GNUC_VER >= 407)
        : public integral_constant<bool, __is_standard_layout(_Tp)>
#else
        : integral_constant<bool, is_scalar<typename remove_all_extents<_Tp>::type>::value>
#endif
        {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_standard_layout_v
        = is_standard_layout<_Tp>::value;
#endif

    // is_trivially_copyable;

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_trivially_copyable
#if __WI_HAS_FEATURE_IS_TRIVIALLY_COPYABLE
        : public integral_constant<bool, __is_trivially_copyable(_Tp)>
#elif __WI_GNUC_VER >= 501
        : public integral_constant<bool, !is_volatile<_Tp>::value && __is_trivially_copyable(_Tp)>
#else
        : integral_constant<bool, is_scalar<typename remove_all_extents<_Tp>::type>::value>
#endif
        {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_trivially_copyable_v
        = is_trivially_copyable<_Tp>::value;
#endif

    // is_trivial;

    template <class _Tp> struct __WI_LIBCPP_TEMPLATE_VIS is_trivial
#if __WI_HAS_FEATURE_IS_TRIVIAL || __WI_GNUC_VER >= 407
        : public integral_constant<bool, __is_trivial(_Tp)>
#else
        : integral_constant<bool, is_trivially_copyable<_Tp>::value &&
                                    is_trivially_default_constructible<_Tp>::value>
#endif
        {};

#if __WI_LIBCPP_STD_VER > 11 && !defined(__WI_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR __WI_LIBCPP_CONSTEXPR bool is_trivial_v
        = is_trivial<_Tp>::value;
#endif

    template <class _Tp> struct __is_reference_wrapper_impl : public false_type {};
    template <class _Tp> struct __is_reference_wrapper_impl<reference_wrapper<_Tp> > : public true_type {};
    template <class _Tp> struct __is_reference_wrapper
        : public __is_reference_wrapper_impl<typename remove_cv<_Tp>::type> {};

#ifndef __WI_LIBCPP_CXX03_LANG

    template <class _Fp, class _A0,
            class _DecayFp = typename decay<_Fp>::type,
            class _DecayA0 = typename decay<_A0>::type,
            class _ClassT = typename __member_pointer_class_type<_DecayFp>::type>
    using __enable_if_bullet1 = typename enable_if
        <
            is_member_function_pointer<_DecayFp>::value
            && is_base_of<_ClassT, _DecayA0>::value
        >::type;

    template <class _Fp, class _A0,
            class _DecayFp = typename decay<_Fp>::type,
            class _DecayA0 = typename decay<_A0>::type>
    using __enable_if_bullet2 = typename enable_if
        <
            is_member_function_pointer<_DecayFp>::value
            && __is_reference_wrapper<_DecayA0>::value
        >::type;

    template <class _Fp, class _A0,
            class _DecayFp = typename decay<_Fp>::type,
            class _DecayA0 = typename decay<_A0>::type,
            class _ClassT = typename __member_pointer_class_type<_DecayFp>::type>
    using __enable_if_bullet3 = typename enable_if
        <
            is_member_function_pointer<_DecayFp>::value
            && !is_base_of<_ClassT, _DecayA0>::value
            && !__is_reference_wrapper<_DecayA0>::value
        >::type;

    template <class _Fp, class _A0,
            class _DecayFp = typename decay<_Fp>::type,
            class _DecayA0 = typename decay<_A0>::type,
            class _ClassT = typename __member_pointer_class_type<_DecayFp>::type>
    using __enable_if_bullet4 = typename enable_if
        <
            is_member_object_pointer<_DecayFp>::value
            && is_base_of<_ClassT, _DecayA0>::value
        >::type;

    template <class _Fp, class _A0,
            class _DecayFp = typename decay<_Fp>::type,
            class _DecayA0 = typename decay<_A0>::type>
    using __enable_if_bullet5 = typename enable_if
        <
            is_member_object_pointer<_DecayFp>::value
            && __is_reference_wrapper<_DecayA0>::value
        >::type;

    template <class _Fp, class _A0,
            class _DecayFp = typename decay<_Fp>::type,
            class _DecayA0 = typename decay<_A0>::type,
            class _ClassT = typename __member_pointer_class_type<_DecayFp>::type>
    using __enable_if_bullet6 = typename enable_if
        <
            is_member_object_pointer<_DecayFp>::value
            && !is_base_of<_ClassT, _DecayA0>::value
            && !__is_reference_wrapper<_DecayA0>::value
        >::type;

    // __invoke forward declarations

    // fall back - none of the bullets

#define __WI_LIBCPP_INVOKE_RETURN(...) \
        __WI_NOEXCEPT_(__WI_NOEXCEPT_(__VA_ARGS__)) -> decltype(__VA_ARGS__) \
        { return __VA_ARGS__; }

    template <class ..._Args>
    auto __invoke(__any, _Args&& ...__args) -> __nat;

    template <class ..._Args>
    auto __invoke_constexpr(__any, _Args&& ...__args) -> __nat;

    // bullets 1, 2 and 3

    template <class _Fp, class _A0, class ..._Args,
            class = __enable_if_bullet1<_Fp, _A0>>
    inline __WI_LIBCPP_INLINE_VISIBILITY
    auto
    __invoke(_Fp&& __f, _A0&& __a0, _Args&& ...__args)
    __WI_LIBCPP_INVOKE_RETURN((wistd::forward<_A0>(__a0).*__f)(wistd::forward<_Args>(__args)...))

    template <class _Fp, class _A0, class ..._Args,
            class = __enable_if_bullet1<_Fp, _A0>>
    inline __WI_LIBCPP_INLINE_VISIBILITY
    __WI_LIBCPP_CONSTEXPR auto
    __invoke_constexpr(_Fp&& __f, _A0&& __a0, _Args&& ...__args)
    __WI_LIBCPP_INVOKE_RETURN((wistd::forward<_A0>(__a0).*__f)(wistd::forward<_Args>(__args)...))

    template <class _Fp, class _A0, class ..._Args,
            class = __enable_if_bullet2<_Fp, _A0>>
    inline __WI_LIBCPP_INLINE_VISIBILITY
    auto
    __invoke(_Fp&& __f, _A0&& __a0, _Args&& ...__args)
    __WI_LIBCPP_INVOKE_RETURN((__a0.get().*__f)(wistd::forward<_Args>(__args)...))

    template <class _Fp, class _A0, class ..._Args,
            class = __enable_if_bullet2<_Fp, _A0>>
    inline __WI_LIBCPP_INLINE_VISIBILITY
    __WI_LIBCPP_CONSTEXPR auto
    __invoke_constexpr(_Fp&& __f, _A0&& __a0, _Args&& ...__args)
    __WI_LIBCPP_INVOKE_RETURN((__a0.get().*__f)(wistd::forward<_Args>(__args)...))

    template <class _Fp, class _A0, class ..._Args,
            class = __enable_if_bullet3<_Fp, _A0>>
    inline __WI_LIBCPP_INLINE_VISIBILITY
    auto
    __invoke(_Fp&& __f, _A0&& __a0, _Args&& ...__args)
    __WI_LIBCPP_INVOKE_RETURN(((*wistd::forward<_A0>(__a0)).*__f)(wistd::forward<_Args>(__args)...))

    template <class _Fp, class _A0, class ..._Args,
            class = __enable_if_bullet3<_Fp, _A0>>
    inline __WI_LIBCPP_INLINE_VISIBILITY
    __WI_LIBCPP_CONSTEXPR auto
    __invoke_constexpr(_Fp&& __f, _A0&& __a0, _Args&& ...__args)
    __WI_LIBCPP_INVOKE_RETURN(((*wistd::forward<_A0>(__a0)).*__f)(wistd::forward<_Args>(__args)...))

    // bullets 4, 5 and 6

    template <class _Fp, class _A0,
            class = __enable_if_bullet4<_Fp, _A0>>
    inline __WI_LIBCPP_INLINE_VISIBILITY
    auto
    __invoke(_Fp&& __f, _A0&& __a0)
    __WI_LIBCPP_INVOKE_RETURN(wistd::forward<_A0>(__a0).*__f)

    template <class _Fp, class _A0,
            class = __enable_if_bullet4<_Fp, _A0>>
    inline __WI_LIBCPP_INLINE_VISIBILITY
    __WI_LIBCPP_CONSTEXPR auto
    __invoke_constexpr(_Fp&& __f, _A0&& __a0)
    __WI_LIBCPP_INVOKE_RETURN(wistd::forward<_A0>(__a0).*__f)

    template <class _Fp, class _A0,
            class = __enable_if_bullet5<_Fp, _A0>>
    inline __WI_LIBCPP_INLINE_VISIBILITY
    auto
    __invoke(_Fp&& __f, _A0&& __a0)
    __WI_LIBCPP_INVOKE_RETURN(__a0.get().*__f)

    template <class _Fp, class _A0,
            class = __enable_if_bullet5<_Fp, _A0>>
    inline __WI_LIBCPP_INLINE_VISIBILITY
    __WI_LIBCPP_CONSTEXPR auto
    __invoke_constexpr(_Fp&& __f, _A0&& __a0)
    __WI_LIBCPP_INVOKE_RETURN(__a0.get().*__f)

    template <class _Fp, class _A0,
            class = __enable_if_bullet6<_Fp, _A0>>
    inline __WI_LIBCPP_INLINE_VISIBILITY
    auto
    __invoke(_Fp&& __f, _A0&& __a0)
    __WI_LIBCPP_INVOKE_RETURN((*wistd::forward<_A0>(__a0)).*__f)

    template <class _Fp, class _A0,
            class = __enable_if_bullet6<_Fp, _A0>>
    inline __WI_LIBCPP_INLINE_VISIBILITY
    __WI_LIBCPP_CONSTEXPR auto
    __invoke_constexpr(_Fp&& __f, _A0&& __a0)
    __WI_LIBCPP_INVOKE_RETURN((*wistd::forward<_A0>(__a0)).*__f)

    // bullet 7

    template <class _Fp, class ..._Args>
    inline __WI_LIBCPP_INLINE_VISIBILITY
    auto
    __invoke(_Fp&& __f, _Args&& ...__args)
    __WI_LIBCPP_INVOKE_RETURN(wistd::forward<_Fp>(__f)(wistd::forward<_Args>(__args)...))

    template <class _Fp, class ..._Args>
    inline __WI_LIBCPP_INLINE_VISIBILITY
    __WI_LIBCPP_CONSTEXPR auto
    __invoke_constexpr(_Fp&& __f, _Args&& ...__args)
    __WI_LIBCPP_INVOKE_RETURN(wistd::forward<_Fp>(__f)(wistd::forward<_Args>(__args)...))

#undef __WI_LIBCPP_INVOKE_RETURN

    // __invokable

    template <class _Ret, class _Fp, class ..._Args>
    struct __invokable_r
    {
        // FIXME: Check that _Ret, _Fp, and _Args... are all complete types, cv void,
        // or incomplete array types as required by the standard.
        using _Result = decltype(
            __invoke(declval<_Fp>(), declval<_Args>()...));

        using type =
            typename conditional<
                !is_same<_Result, __nat>::value,
                typename conditional<
                    is_void<_Ret>::value,
                    true_type,
                    is_convertible<_Result, _Ret>
                >::type,
                false_type
            >::type;
        static const bool value = type::value;
    };

    template <class _Fp, class ..._Args>
    using __invokable = __invokable_r<void, _Fp, _Args...>;

    template <bool _IsInvokable, bool _IsCVVoid, class _Ret, class _Fp, class ..._Args>
    struct __nothrow_invokable_r_imp {
    static const bool value = false;
    };

    template <class _Ret, class _Fp, class ..._Args>
    struct __nothrow_invokable_r_imp<true, false, _Ret, _Fp, _Args...>
    {
        typedef __nothrow_invokable_r_imp _ThisT;

        template <class _Tp>
        static void __test_noexcept(_Tp) noexcept;

        static const bool value = noexcept(_ThisT::__test_noexcept<_Ret>(
            __invoke(declval<_Fp>(), declval<_Args>()...)));
    };

    template <class _Ret, class _Fp, class ..._Args>
    struct __nothrow_invokable_r_imp<true, true, _Ret, _Fp, _Args...>
    {
        static const bool value = noexcept(
            __invoke(declval<_Fp>(), declval<_Args>()...));
    };

    template <class _Ret, class _Fp, class ..._Args>
    using __nothrow_invokable_r =
        __nothrow_invokable_r_imp<
                __invokable_r<_Ret, _Fp, _Args...>::value,
                is_void<_Ret>::value,
                _Ret, _Fp, _Args...
        >;

    template <class _Fp, class ..._Args>
    using __nothrow_invokable =
        __nothrow_invokable_r_imp<
                __invokable<_Fp, _Args...>::value,
                true, void, _Fp, _Args...
        >;

    template <class _Fp, class ..._Args>
    struct __invoke_of
        : public enable_if<
            __invokable<_Fp, _Args...>::value,
            typename __invokable_r<void, _Fp, _Args...>::_Result>
    {
    };

    // result_of

    template <class _Fp, class ..._Args>
    class __WI_LIBCPP_TEMPLATE_VIS result_of<_Fp(_Args...)>
        : public __invoke_of<_Fp, _Args...>
    {
    };

#if __WI_LIBCPP_STD_VER > 11
    template <class _Tp> using result_of_t = typename result_of<_Tp>::type;
#endif

#if __WI_LIBCPP_STD_VER > 14

    // invoke_result

    template <class _Fn, class... _Args>
    struct __WI_LIBCPP_TEMPLATE_VIS invoke_result
        : __invoke_of<_Fn, _Args...>
    {
    };

    template <class _Fn, class... _Args>
    using invoke_result_t = typename invoke_result<_Fn, _Args...>::type;

    // is_invocable

    template <class _Fn, class ..._Args>
    struct __WI_LIBCPP_TEMPLATE_VIS is_invocable
        : integral_constant<bool, __invokable<_Fn, _Args...>::value> {};

    template <class _Ret, class _Fn, class ..._Args>
    struct __WI_LIBCPP_TEMPLATE_VIS is_invocable_r
        : integral_constant<bool, __invokable_r<_Ret, _Fn, _Args...>::value> {};

    template <class _Fn, class ..._Args>
    __WI_LIBCPP_INLINE_VAR constexpr bool is_invocable_v
        = is_invocable<_Fn, _Args...>::value;

    template <class _Ret, class _Fn, class ..._Args>
    __WI_LIBCPP_INLINE_VAR constexpr bool is_invocable_r_v
        = is_invocable_r<_Ret, _Fn, _Args...>::value;

    // is_nothrow_invocable

    template <class _Fn, class ..._Args>
    struct __WI_LIBCPP_TEMPLATE_VIS is_nothrow_invocable
        : integral_constant<bool, __nothrow_invokable<_Fn, _Args...>::value> {};

    template <class _Ret, class _Fn, class ..._Args>
    struct __WI_LIBCPP_TEMPLATE_VIS is_nothrow_invocable_r
        : integral_constant<bool, __nothrow_invokable_r<_Ret, _Fn, _Args...>::value> {};

    template <class _Fn, class ..._Args>
    __WI_LIBCPP_INLINE_VAR constexpr bool is_nothrow_invocable_v
        = is_nothrow_invocable<_Fn, _Args...>::value;

    template <class _Ret, class _Fn, class ..._Args>
    __WI_LIBCPP_INLINE_VAR constexpr bool is_nothrow_invocable_r_v
        = is_nothrow_invocable_r<_Ret, _Fn, _Args...>::value;

#endif // __WI_LIBCPP_STD_VER > 14

#endif  // !defined(__WI_LIBCPP_CXX03_LANG)

    template <class _Tp> struct __is_swappable;
    template <class _Tp> struct __is_nothrow_swappable;

    template <class _Tp>
    inline __WI_LIBCPP_INLINE_VISIBILITY
#ifndef __WI_LIBCPP_CXX03_LANG
    typename enable_if
    <
        is_move_constructible<_Tp>::value &&
        is_move_assignable<_Tp>::value
    >::type
#else
    void
#endif
    swap_wil(_Tp& __x, _Tp& __y) __WI_NOEXCEPT_(is_nothrow_move_constructible<_Tp>::value &&
                                          is_nothrow_move_assignable<_Tp>::value)
    {
        _Tp __t(wistd::move(__x));
        __x = wistd::move(__y);
        __y = wistd::move(__t);
    }

    template <class _ForwardIterator1, class _ForwardIterator2>
    inline __WI_LIBCPP_INLINE_VISIBILITY
    _ForwardIterator2
    swap_ranges_wil(_ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2)
    {
        for(; __first1 != __last1; ++__first1, (void) ++__first2)
            swap_wil(*__first1, *__first2);
        return __first2;
    }

    template<class _Tp, size_t _Np>
    inline __WI_LIBCPP_INLINE_VISIBILITY
    typename enable_if<
        __is_swappable<_Tp>::value
    >::type
    swap_wil(_Tp (&__a)[_Np], _Tp (&__b)[_Np]) __WI_NOEXCEPT_(__is_nothrow_swappable<_Tp>::value)
    {
        wistd::swap_ranges_wil(__a, __a + _Np, __b);
    }

    template <class _ForwardIterator1, class _ForwardIterator2>
    inline __WI_LIBCPP_INLINE_VISIBILITY
    void
    iter_swap_wil(_ForwardIterator1 __a, _ForwardIterator2 __b)
        //                                  __WI_NOEXCEPT_(__WI_NOEXCEPT_(swap_wil(*__a, *__b)))
                __WI_NOEXCEPT_(__WI_NOEXCEPT_(swap_wil(*declval<_ForwardIterator1>(),
                                                   *declval<_ForwardIterator2>())))
    {
        swap_wil(*__a, *__b);
    }

    // __swappable

    namespace __detail
    {
        // ALL generic swap overloads MUST already have a declaration available at this point.

        template <class _Tp, class _Up = _Tp,
                bool _NotVoid = !is_void<_Tp>::value && !is_void<_Up>::value>
        struct __swappable_with
        {
            template <class _LHS, class _RHS>
            static decltype(swap_wil(declval<_LHS>(), declval<_RHS>()))
            __test_swap(int);
            template <class, class>
            static __nat __test_swap(long);

            // Extra parens are needed for the C++03 definition of decltype.
            typedef decltype((__test_swap<_Tp, _Up>(0))) __swap1;
            typedef decltype((__test_swap<_Up, _Tp>(0))) __swap2;

            static const bool value = !is_same<__swap1, __nat>::value
                                && !is_same<__swap2, __nat>::value;
        };

        template <class _Tp, class _Up>
        struct __swappable_with<_Tp, _Up,  false> : false_type {};

        template <class _Tp, class _Up = _Tp, bool _Swappable = __swappable_with<_Tp, _Up>::value>
        struct __nothrow_swappable_with {
        static const bool value =
#ifndef __WI_LIBCPP_HAS_NO_NOEXCEPT
            noexcept(swap_wil(declval<_Tp>(), declval<_Up>()))
        &&  noexcept(swap_wil(declval<_Up>(), declval<_Tp>()));
#else
            false;
#endif
        };

        template <class _Tp, class _Up>
        struct __nothrow_swappable_with<_Tp, _Up, false> : false_type {};

    }  // __detail

    template <class _Tp>
    struct __is_swappable
        : public integral_constant<bool, __detail::__swappable_with<_Tp&>::value>
    {
    };

    template <class _Tp>
    struct __is_nothrow_swappable
        : public integral_constant<bool, __detail::__nothrow_swappable_with<_Tp&>::value>
    {
    };

#if __WI_LIBCPP_STD_VER > 14

    template <class _Tp, class _Up>
    struct __WI_LIBCPP_TEMPLATE_VIS is_swappable_with
        : public integral_constant<bool, __detail::__swappable_with<_Tp, _Up>::value>
    {
    };

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_swappable
        : public conditional<
            __is_referenceable<_Tp>::value,
            is_swappable_with<
                typename add_lvalue_reference<_Tp>::type,
                typename add_lvalue_reference<_Tp>::type>,
            false_type
        >::type
    {
    };

    template <class _Tp, class _Up>
    struct __WI_LIBCPP_TEMPLATE_VIS is_nothrow_swappable_with
        : public integral_constant<bool, __detail::__nothrow_swappable_with<_Tp, _Up>::value>
    {
    };

    template <class _Tp>
    struct __WI_LIBCPP_TEMPLATE_VIS is_nothrow_swappable
        : public conditional<
            __is_referenceable<_Tp>::value,
            is_nothrow_swappable_with<
                typename add_lvalue_reference<_Tp>::type,
                typename add_lvalue_reference<_Tp>::type>,
            false_type
        >::type
    {
    };

    template <class _Tp, class _Up>
    __WI_LIBCPP_INLINE_VAR constexpr bool is_swappable_with_v
        = is_swappable_with<_Tp, _Up>::value;

    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR constexpr bool is_swappable_v
        = is_swappable<_Tp>::value;

    template <class _Tp, class _Up>
    __WI_LIBCPP_INLINE_VAR constexpr bool is_nothrow_swappable_with_v
        = is_nothrow_swappable_with<_Tp, _Up>::value;

    template <class _Tp>
    __WI_LIBCPP_INLINE_VAR constexpr bool is_nothrow_swappable_v
        = is_nothrow_swappable<_Tp>::value;

#endif // __WI_LIBCPP_STD_VER > 14

#ifdef __WI_LIBCPP_UNDERLYING_TYPE

    template <class _Tp>
    struct underlying_type
    {
        typedef __WI_LIBCPP_UNDERLYING_TYPE(_Tp) type;
    };

#if __WI_LIBCPP_STD_VER > 11
    template <class _Tp> using underlying_type_t = typename underlying_type<_Tp>::type;
#endif

#else  // __WI_LIBCPP_UNDERLYING_TYPE

    template <class _Tp, bool _Support = false>
    struct underlying_type
    {
        static_assert(_Support, "The underyling_type trait requires compiler "
                                "support. Either no such support exists or "
                                "libc++ does not know how to use it.");
    };

#endif // __WI_LIBCPP_UNDERLYING_TYPE


    template <class _Tp, bool = is_enum<_Tp>::value>
    struct __sfinae_underlying_type
    {
        typedef typename underlying_type<_Tp>::type type;
        typedef decltype(((type)1) + 0) __promoted_type;
    };

    template <class _Tp>
    struct __sfinae_underlying_type<_Tp, false> {};

    inline __WI_LIBCPP_INLINE_VISIBILITY __WI_LIBCPP_CONSTEXPR
    int __convert_to_integral(int __val) { return __val; }

    inline __WI_LIBCPP_INLINE_VISIBILITY __WI_LIBCPP_CONSTEXPR
    unsigned __convert_to_integral(unsigned __val) { return __val; }

    inline __WI_LIBCPP_INLINE_VISIBILITY __WI_LIBCPP_CONSTEXPR
    long __convert_to_integral(long __val) { return __val; }

    inline __WI_LIBCPP_INLINE_VISIBILITY __WI_LIBCPP_CONSTEXPR
    unsigned long __convert_to_integral(unsigned long __val) { return __val; }

    inline __WI_LIBCPP_INLINE_VISIBILITY __WI_LIBCPP_CONSTEXPR
    long long __convert_to_integral(long long __val) { return __val; }

    inline __WI_LIBCPP_INLINE_VISIBILITY __WI_LIBCPP_CONSTEXPR
    unsigned long long __convert_to_integral(unsigned long long __val) {return __val; }

    template<typename _Fp>
    inline __WI_LIBCPP_INLINE_VISIBILITY __WI_LIBCPP_CONSTEXPR
    typename enable_if<is_floating_point<_Fp>::value, long long>::type
    __convert_to_integral(_Fp __val) { return __val; }

#ifndef __WI_LIBCPP_HAS_NO_INT128
    inline __WI_LIBCPP_INLINE_VISIBILITY __WI_LIBCPP_CONSTEXPR
    __int128_t __convert_to_integral(__int128_t __val) { return __val; }

    inline __WI_LIBCPP_INLINE_VISIBILITY __WI_LIBCPP_CONSTEXPR
    __uint128_t __convert_to_integral(__uint128_t __val) { return __val; }
#endif

    template <class _Tp>
    inline __WI_LIBCPP_INLINE_VISIBILITY __WI_LIBCPP_CONSTEXPR
    typename __sfinae_underlying_type<_Tp>::__promoted_type
    __convert_to_integral(_Tp __val) { return __val; }

#ifndef __WI_LIBCPP_CXX03_LANG

    template <class _Tp>
    struct __has_operator_addressof_member_imp
    {
        template <class _Up>
            static auto __test(int)
                -> typename __select_2nd<decltype(declval<_Up>().operator&()), true_type>::type;
        template <class>
            static auto __test(long) -> false_type;

        static const bool value = decltype(__test<_Tp>(0))::value;
    };

    template <class _Tp>
    struct __has_operator_addressof_free_imp
    {
        template <class _Up>
            static auto __test(int)
                -> typename __select_2nd<decltype(operator&(declval<_Up>())), true_type>::type;
        template <class>
            static auto __test(long) -> false_type;

        static const bool value = decltype(__test<_Tp>(0))::value;
    };

    template <class _Tp>
    struct __has_operator_addressof
        : public integral_constant<bool, __has_operator_addressof_member_imp<_Tp>::value
                                    || __has_operator_addressof_free_imp<_Tp>::value>
    {};

#endif  // __WI_LIBCPP_CXX03_LANG

#ifndef __WI_LIBCPP_CXX03_LANG

    template <class...> using void_t = void;

# ifndef __WI_LIBCPP_HAS_NO_VARIADICS
    template <class... _Args>
    struct conjunction : __and_<_Args...> {};
    template<class... _Args>
    __WI_LIBCPP_INLINE_VAR constexpr bool conjunction_v
        = conjunction<_Args...>::value;

    template <class... _Args>
    struct disjunction : __or_<_Args...> {};
    template<class... _Args>
    __WI_LIBCPP_INLINE_VAR constexpr bool disjunction_v
        = disjunction<_Args...>::value;

    template <class _Tp>
    struct negation : __not_<_Tp> {};
    template<class _Tp>
    __WI_LIBCPP_INLINE_VAR constexpr bool negation_v
        = negation<_Tp>::value;
# endif // __WI_LIBCPP_HAS_NO_VARIADICS
#endif  // __WI_LIBCPP_CXX03_LANG

    // These traits are used in __tree and __hash_table
#ifndef __WI_LIBCPP_CXX03_LANG
    struct __extract_key_fail_tag {};
    struct __extract_key_self_tag {};
    struct __extract_key_first_tag {};

    template <class _ValTy, class _Key,
            class _RawValTy = typename __unconstref<_ValTy>::type>
    struct __can_extract_key
        : conditional<is_same<_RawValTy, _Key>::value, __extract_key_self_tag,
                    __extract_key_fail_tag>::type {};

    template <class _Pair, class _Key, class _First, class _Second>
    struct __can_extract_key<_Pair, _Key, pair<_First, _Second>>
        : conditional<is_same<typename remove_const<_First>::type, _Key>::value,
                    __extract_key_first_tag, __extract_key_fail_tag>::type {};

    // __can_extract_map_key uses true_type/false_type instead of the tags.
    // It returns true if _Key != _ContainerValueTy (the container is a map not a set)
    // and _ValTy == _Key.
    template <class _ValTy, class _Key, class _ContainerValueTy,
            class _RawValTy = typename __unconstref<_ValTy>::type>
    struct __can_extract_map_key
        : integral_constant<bool, is_same<_RawValTy, _Key>::value> {};

    // This specialization returns __extract_key_fail_tag for non-map containers
    // because _Key == _ContainerValueTy
    template <class _ValTy, class _Key, class _RawValTy>
    struct __can_extract_map_key<_ValTy, _Key, _Key, _RawValTy>
        : false_type {};

#endif

#if __WI_LIBCPP_STD_VER > 17
    enum class endian
    {
        little = 0xDEAD,
        big    = 0xFACE,
#if defined(__WI_LIBCPP_LITTLE_ENDIAN)
        native = little
#elif defined(__WI_LIBCPP_BIG_ENDIAN)
        native = big
#else
        native = 0xCAFE
#endif
    };
#endif
}
/// @endcond

#endif // _WISTD_TYPE_TRAITS_H_
